Improve the SimpleTest documentation

This patch does the following:

- Rewrites INSTALL.txt
- Fixes various inaccuracies in README.txt.
- Adds an admin/help/simpletest page that explains how to use the module.
- Adds a handbook page at http://drupal.org/handbook/modules/simpletest with the contents of this page (for consistency with other modules, as well as for easy review :)).
- Changes the titles on the main SimpleTest page to just "SimpleTest", for consistency with other modules.

INSTALL.txt before:

Install
-----------------------

- Copy this module package to your modules directory
- Install the simpletest framework to a new subdirectory of simpletest module: modules/simpletest/simpletest
  You can find it at https://sourceforge.net/project/showfiles.php?group_id=76550
- At least Version 1.0.1 alpha3 of the simpletest framework is required (for upload tests).
- Activate the simpletest.module
- Visit the admin/simpletest page

INSTALL.txt after:

$Id$

Installation
------------
1. Uncompress the SimpleTest module package to your sites/all/modules directory.
2. Download the latest SimpleTest package from SourceForge.net:
   https://sourceforge.net/project/showfiles.php?group_id=76550&package_id=77275
   Note: At least version 1.0.1 alpha3 is required (for upload tests)
3. Uncompress it inside your SimpleTest module directory:
   sites/all/modules/simpletest/simpletest
4. Go to Administer >> Site Building >> Modules (admin/build/modules) and
   enable the SimpleTest module.
5. Go to Administer >> Site building >> SimpleTest (admin/build/simpletest) to
   begin using the module.
6. (Optional) Go to Administer >> Help >> SimpleTest (admin/help/simpletest) fo
   more information on how to use the SimpleTest module.
7. (Optional) Go to Administer >> Site configuration >> SimpleTest
   (admin/settings/simpletest) to configure advanced settings.

admin/help/simpletest:
See http://drupal.org/handbook/modules/simpletest. Please make any edits there directly, and I can get them incorporated into the patch.

Old README.txt:

Description
-----------------------
A framework for running unit tests in Drupal.

USAGE WARNING
-----------------------
NEVER USE THIS MODULE IN A PRODUCTION ENVIRONMENT!
While running a test this module may (completely) change your Drupal setup.
Though it usually recovers the original setup at the end of a test, there is
no guarantee that it will work correctly, especially if an error or timeout
occurs.

Since all registered users have the registered users role this role
MUST have the default settings for current tests to run correct.
This also applies for anonymous user.


Status
-----------------------
Some core tests have been written - see the /tests subdirectory. We need more,
especially for contributed modules.

Simpletest hook
-----------------------
This module offers a new 'simpletest' hook. Modules implementing this hook should return an array of paths which
point to test files. These paths should be relative to the /simpletest directory.

Writing Tests
-----------------------
Please write some tests.
See http://drupal.org/simpletest

Authors
-----------------------
Moshe Weitzman < weitzman at tejasa dot com >
Kuba Zygmunt   < kuba.zygmunt at gmail dot com >
Thomas Ilsche  < ThomasIlsche at gmx dot de >

Thanks
-----------------------
to Google for sponsoring the testsuite Summer of Code project.
see http://code.google.com/summerofcode.html

New README.txt:

$Id$

Description
-----------
A framework for running unit tests in Drupal.

USAGE WARNING
-------------
NEVER USE THIS MODULE IN A PRODUCTION ENVIRONMENT!
While running a test this module may (completely) change your Drupal setup.
Though it usually recovers the original setup at the end of a test, there is
no guarantee that it will work correctly, especially if an error or timeout
occurs.

Status
------
Drupal core tests are in the /tests subdirectory. We need people to help
expand our library of core tests, as well as provide tests for contributed
modules.

Documentation
-------------
* Official SimpleTest documentation:
  http://simpletest.org/en/start-testing.html
* SimpleTest module API documentation:
  http://drupal.org/simpletest
* An Introduction to Unit Testing in Drupal:
  http://www.lullabot.com/articles/introduction-unit-testing
* A Drupal Module Developer's Guide to SimpleTest:
  http://www.lullabot.com/articles/drupal-module-developer-guide-simpletest

Module Authors
--------------
* Moshe Weitzman < weitzman at tejasa dot com >
* Kuba Zygmunt   < kuba.zygmunt at gmail dot com >
* Thomas Ilsche  < ThomasIlsche at gmx dot de >
* Rok Zlender    < rok.zlender at gmail dot com >

Thanks
------
* Google for sponsoring the initial test suite (and subsequent improvements)
  as Summer of Code projects:
  http://code.google.com/soc/
* Google and all students/mentors involved in the creation of a huge set of
  core tests during the Google Highly Open Participation contest:
  http://code.google.com/opensource/ghop/

If you know of any other documentation resources, please let me know so we can get them added! The point of this patch is to make it as simple as possible for someone who wants to figure out what all this SimpleTest stuff is all about to do so quickly.

(note: the weirdness of the thing after the URL being displayed right after the URL is some weird codefilter bug; not in the actual text)

The API docs need a lot of love, but I'll handle that separately. In the meantime, reviews of this would be greatly appreciated!