[FR-devel] Added new plugin

[Rich Kilmer]

Added new KeyManager plugin under the System_Commands subsystem.  I was
getting a bit worried that we had all these key bindings mixed into
defining commands for menus...so I created the KeyManager to manage
Commands to Keys.

Usage:

key_mgr = plugin['/system/ui/keys'].manager

key_mgr.bind("App/File/Open", :ctrl, :O)

and...

keys = key_mgr.get_binding("App/File/Open")
# keys = [:ctrl, :O]

The three modifiers it knows about are :alt, :ctrl and :shift.

The bindings are stored as subslots like:

plugin['/system/ui/keys/Ctrl/Shift/S'].data #=> 'App/File/SaveAs'

The centralization of key to command mappings will allow us to create a
tool for the user to use to map keys.  Also, non menu-based commands
will be able to be executed by mapping keys.  This will enable simple
macro capabilities.

Will now move over to the Debugger and DockPane...I promise ;-)

-rich