Update to SignalR 2.0.1; automate future updates

This PR updates SignalR to version 2.0.1 and adds some scripts that automatically grab the latest SignalR.JS package and update the bower package version.

The scripts are a combination of msbuild and shell (perl/sed). There may be a simpler way of updating bower.json but I couldn't think of one that works in mono xbuild as well as msbuild.