Adding support for TFS prompt

I have created an initial TFS prompt, and updated the readme.

With this PR the prompt will appear as follows:
C:\Projects [+0 ~2 -0 | 1:(+0 ~8 -0)]>

Which gives an indication of both the local pending changes, and changes not yet retrieved from TFS.

I investigated the use of the TFS Powershell commandlets, however that would require an additional dependency.

I added 2 .tfc files which are executed by the TF command. By issuing all the commands via the .tfc file, we avoid multiple NTLM handshakes, which improves overall performance.