Add keyboard shortcuts

[finger563]

for copy / cut / paste / instance / move

will help with the same use-cases as #29

Is now possible because we support multi-select, but will need to figure out how we should handle disjoint set pasting /instancing / moving. especially with respect to how pointers are updated or not updated. Thankfully we have some utility functions (as does cytoscape) for determining neighborhoods, so that's a good place to start.

[finger563]

related to #60 and webgme/webgme#1537