Following the proposed mockups, the shortcut list must
have the ability to reset modified to non-default shortcuts
right from the listbox.
After adding the necessary API in CcKeyboardItem, adding
the user-visible elements to enable that is easy.
To make that happen, add a button that resets the
keyboard shortcut.
https://bugzilla.gnome.org/show_bug.cgi?id=769063
The collision detection code was removed in commit a0a155884e
as the cleanup was happening because the previous code was closely
tied to the user interface components.
Because that code wasn't appliable to the new listbox UI, it was
temporarily removed.
This patch re-adds this feature to work with the new code orgazination.
https://bugzilla.gnome.org/show_bug.cgi?id=769063
Instead of having CcKeyboardPanel managing both UI and backend code,
factor the backend code to a new CcKeyboardManager class and drop
backend management from the panel itself.
The new backend class handles the loading, creation and removal and
search of keyboard shortcuts. It also resolves reversible shortcuts
when searching.
This patch moves the code to this new class, and updates the rest of
the Keyboard panel to use it instead.
https://bugzilla.gnome.org/show_bug.cgi?id=769063
