Revert "Temporarily remove content-permissions test add-on till Bug 1094068 is fixed. a=@gozala"

This reverts commit 07c466d8dc061c511627c517ed95b555a4c0cf73.
Bug 1089236: Disabel failing tests.
bug 1090135 - use nsIDOMWindowUtils::loadSheetUsingURIString
Work in progress.
Fix most edge cases.
Wire events to context-menu items.
Fix the way context-menu handles registry.
Get rid of annoying dead object errors.
Wrap shared Item and Menu APIs into disposables so they unloaded with addons.
Add support for required contexts.
Update generated class names.
Update html writer.
Remove logging.
Add more tests.
Simplify existing tests.
Fix a spelling of seperator.
Fix the Page context & isPage reader.
Add tests for page contexts.
Add test for page context with selection.
Add test for selection context.