Adding hotkeys for authoring Touch UI. Fixes #248.

Added support for hotkeys in touch ui. 

ctrl+shift+e for edit layer
ctrl+shift+p for preview layer
ctrl+shift+a for annotate layer
ctrl+shift+d for developer layer
ctrl+shift+t for targeting layer
ctrl+shift+s to toggle sidepanel
Does this need to be in the `cq.authoring.editor` category? It looks like this is included by way of `/switchlayers` clientlib which is part of the `cq.authoring.editor` clientlib already?