Add ability to have cake kill any processes using the .exe or .dll before relinking

[lewissbaker]

On Windows when you run through an edit/compile/debug cycle often it can be quite annoying having build failures due to the linker not being able to write to the .dll or .exe target because they are currently in use by a running process (typically the process you were just using to test/debug).

It save some developer frustration and time if cake could be configured to automatically find all processes that currently have a .dll/.exe loaded and kill those processes before running the linker.