Keyboard shortcuts: Integrate with compositor.

[Sammy99jsp]

• Add keyboard shortcuts to the default config.
• Parse the keyboard shortcuts into the combinations of ModifierState and key-codes (u32s)
• Incorporate these into the compositor, with a friendly interface.

[Sammy99jsp]

Such an interface could be an extension to the ConfigurationSection macro, combined with a revision to AvKeys.

[Sammy99jsp]

In terms of code, we need:

• Uncomplicated syntax
• Easily Expandable
• Integrate with our configuration system
• Be interoperable with xkbcommon

[Sammy99jsp]

So, I am proposing:

• An enum AvKey -- Represents a key (Key(...)); a key parameter Parameter(AvKeyParam); or a raw X11 keycode (X11(u32))).
• An enum AvKeyParam to represent the key parameters.
• A trait (AvKeyShortcut),
• An attribute macro AvShortcut.

The AvShortcut macro generates an implementation of AvKeyShortcut for a particular action:

#[AvShortcut(Logo+{d})]
fn switch_window<B: 'static>(state : &mut Navda<B>, params : &[AvKeyParam]) {
    state.space.elements().nth(params[0].value()).focus();
}