Use TFS Local Workspaces instead of TFS Server

[nag5000]

Rewrite the code to use Local Workspaces instead of TFS Server. The current functionality can be kept optionally.

Problems of the current implementation:

1. High load on the server. Extension periodically sends a request to check for a new version of the file and downloaded it again, if it have changed. If you have opened a lot of documents, the load is high.
2. Some TFS API methods are slow. So, code difficult to read and maintain - there are a lot of asynchronous calls and critical sections (locks).

Complexity of the task that TFS Local Workspace API is badly documented. It isn't clear how to get access to the cached files in the $tf folder, or how to compare files in the Local Workspace without making a request to the server.

[mrubinstein-zz]

Right on. Can't use it in the current form, because i need it to show the differences relative to my workspace version and not latest version in TFS.