Merge pull request #55 from vasily-kirichenko/master

First cut on rename refactoring
Add menu key bindings and rename validation

Use Ctrl + R, Ctrl + N key binding since Ctrl + R, Ctrl + R is magically
disabled.

Add some simple validation to avoid invalid names.
Support renaming multiple documents

Holy shit, it works now.
fix: FSharpVSPowerTools.Logic and FSharpXmlDoc projects don't build without VS 2012 installed