Cleaned up exe names

• Renamed "avrenderer.exe" to "aardvarkxr.exe" #147 - This make it easier to understand what's going on in task manager.
• Renamed the copy of "node.exe" that Aardvark installs to "aardvark_server.exe" to make it easier to find in task manager (and to enable the next thing.
• Added code to kill aardvark_server.exe any time that aardvarkxr.exe is about to start it. This should clean up all the times when normal users will have a stuck server blocking startup. #106
• Changed the aardvark server to listen on localhost so that it won't allow connections to come in from other machines (and won't need a firewall hole punched for it.