implement insert by middle mouse button
Merge remote-tracking branch 'mikhail-m1/master' into fixes-manual-merge
Minor cleanup on patch

Needed to fix a couple failing unit tests and build warnings.  Also made
the past operation much more direct.  In the previous version 'paste'
was implemented by asking vim to run the keystroke 'P'.  This would fail
to paste if the user had previously mapped 'P' to another key and it
could also potentially mess up a current recording session for macros.
Instead i exposed the ICommandUtil interface and just ran paste
directly.