re-adding caretUndoStack.push() and caretRedoStack.clear() calls to fix
bug #707
Merge branch 'master' of https://github.com/joshgiesbrecht/processing
fixing bug #1781 (installing modes/tools on Win)
changes a rename/move to a copy and delete
pulls the delete step out one level so that we can unload the temp
'newContrib' first, since having it loaded was locking the files from
being renamed/removed on Windows (somewhat erratically).

A bit slower than before but should work a heck of a lot more
often for Windows users.
Merge pull request #1847 from joshgiesbrecht/master

fixing bugs #707 and #1781