Add option when loading a keymap clears existing shortcuts before loading new ones.

[PLyczkowski]

Currently it just overrides the currently loaded shortcuts.

It should leave the addon keymap intact though.

[julianeisel]

I just created a patch to make this possible: http://hastebin.com/icilageviq.mel So if you use kc.keymaps.new(... , empty=True) It creates an entirely new keymap instead of overwriting the changed shortcuts.