Replaced old imce integration with BUEditors own. Removed old IE browser support. Added standard classes to field elements, e.g. form-text. Removed help and cancel buttons in dialogs. Made DefinitionList dialog in to a table like the others.

[task] #624596 by ufku, solipsist: Introduces support for BUEditor 2.0 as well as several minor improvements.

Feature: Implements hook_enable() and hook_disable() to update available buttons when modules are enabled/disabled

 - Committed version 1.0

 - Fixed: A bug causing IMCE "Browse..." button not to show due to checking for a non-existing permission.
 - Added: Improved installer that keeps track of dependencies without limiting the site admin's options with regards to altering button icons and titles.

   to have text, they can now be created without any pre-typed link text.
 - Fixed: IMCE file browser dialog now opens when clicking "Browse...".
 - Added: Installer now updates button JS code in case the site path changes
   or the module configuration changes in a way that affects Markdown Editor.

   the module's installed handles everything.
 - Fixed: Updated CSS to work with new BUE dialog markup.

Improved instructions in INSTALL.txt
General code clean-up