Skeleton commit window server

This allows the commit command line tool to open a window as “native”.

We use distributed objects for talking to TextMate and getting a response. For the response, we release the connection in the next iteration of the event loop and then gracefully exit the program. Though it’s not clear if this is enough time for distributed objects to reply the client (if not, an exception is thrown in the client about “connection disappeared while waiting for a reply”).
New (native) commit window

This is based on the previous commit window code base. It replaces the NSTextView with a OakTextView for entering the commit messages. This allows us to take advantage of some of the git grammar features, e.g., fixup!.

If other SCM bundles are updated in the future to include any specific grammars, these can be used in the commit window by setting the bundle grammar to "text.SCM-commit", where SCM could be hg or svn for example.

Changes to note:

	*  The Modify row button for the "--action-cmd" commands are now implemented in the action menu and the table context menu.

	*  The shortcut for committing is ⌘↩ (but fn-return seems to (still) work).
Rework command execution (diff, revert, etc.)

I wanted to get rid of calling /usr/bin/which but ended up also modifying the methods that used the absolutePathForPath: method.