Rename Tracker add-ons to remove shortcut suffix
Shortcut add-on: change to accomodate tracker add-ons

* Ignore shortcuts regardings tracker add-ons. Its settings file is now shared
with Tracker, and those are now handled by Tracker.
* Use a BPathMonitor as specified in a TODO to check the presence and changes on
the settings file. (#6278)
* Use a message to ask Tracker to launch/open folders as specified in TODO
Tracker addons: strip shortcut from name, instead use resource
Tracker: store default add-ons shortcuts in resource

* Default shortcuts for add-ons are now stored within the binary as a resource
(it was previously appended to the file name, as Open Terminal-T, for example)
* Use ~/config/shortcuts_settings to override those default shortcuts
(editable with Shortcuts preflet)
* Tracker avoid rescanning the add-ons directories when unnecessary
* Monitor the shortcuts_settings to apply changes on the fly
* Fallback to default shortcuts whenever appropriate (settings file deleted, etc.)
* Should fix #4446 (with resource rather than attributes)