Removed some leftover debugging code

This commit also fixes a minor problem in the manifest introduced by the
last commit
Added some more utility methods to the CoqTopIdeSlave_v20120710 trait

The trait now has some convenience methods for retrieving option states and
values
Removed the extra option cache from ToggleCoqFlagHandler

OptionalCoqTopIdeSlave_v20120710 already implements an option cache:
there's no good reason to have another one in the handler
Added a keyboard shortcut for the "Set Printing Implicit" command
Added a refreshElements method to the UIUtils class

The second argument of ICommandService.refreshElements isn't exposed by
this method, because Kopitiam doesn't need it (yet)
Added a hook to EditorHandler for detecting when the active editor changes

Some handlers need to update their state -- or the state of their
associated UI elements -- when the editor changes. This hook makes that
easy
Update ToggleCoqFlagHandler's UI elements when the active editor changes