otextensions added - Move OTSocket / ZMQ in new lib

We want to use the minimum of OT in the audit server, so OTSocket (transport class (ZMQ)) should not be part of otlib.

As OTSocket is used by the server and the OTAPI we've decided to add an extra layer. There might be other stuff we move there too later if there is something that is not needed in audit server / not part of the OT core functionality.

This is not changing any of Erics files (in his PR). I'm ok with rebasing if his PR gets merged first.

This will break the .vcproj / MSVC build system.