srv-less: Implements new (v2) API

* Fixes breaking changes for lessc.
* Explicitly remove .tscache on PreBuild.
* Fixes ServerBase and derived types.
* Renames libsass binding folder.
* Code formatting.

.. and code analysis warning fixes.

Fixes at least two issue: https://github.com/madskristensen/WebEssentials2013/issues/1664 and https://github.com/madskristensen/WebEssentials2013/issues/1665.
@SLaks, I tried to Exclude it via proj file but it doesn't recognize any of these patterns: `**/.tscache/**`, `**\.tscache\**`, `**tscache/**` or `**\*tscache/**`. It seems like it has issues recognizing folder names starting with period `.`.