Refactoring + New JS engine + Page visibility settings feature + Works on all page types

I am submitting a patch which brings the following changes:

* Refactoring:
a. introduced template files for including the inline javascript code required to display the Feedback link
b. "humanised" labels in the admin settings forms
c. removed all unnecessary check_plain function calls
d. introduced a static array to store default values for all the opinionlab variables/settings

* Fixing:
a. the permission exported by the hook_perm was using a capital "O" for opinionlab, but throughout the code the checks were made against a fully lowercase permission string. Plus, capitals in permission strings are not allowed by Drupal coding standards;
b. the Floating link wasn't displaying at all with Firefox 3.x on Mac. A new version of the engine (oo_engine_c.js) has been included, which fixes this problem.

* Features:
a. the link can now be displayed on all kind of pages, not just nodes (achieved by moving drupal_add_js into the hook_footer)
b. page visibility settings: in the general settings there is also this new feature which works similarly to the homonymous setting implemented for core blocks. Default value for this is to display the link everywhere but on admin pages (admin/* node/add/* node/*/edit)

Cheers,

Vincenzo