Rationalize and update VS projects and create NuGet packaging.

This change creates a rationalized set of project and solution files for VS 2013/12/10 and cleans up the more distinct VS2008 project. Packaging added and [deployed](https://www.nuget.org/packages/czmq_vc120/) with fix to NuGet targets injection. Also a change to eliminate use of conditional text APIs using unconditional parameterization.