Better Visual Studio 2013 support

**Changes**

 * Update `.cmake` files to find _yaml-cpp_ better on Windows
 * Fix use of insecure `sprintf` over `snprintf`
 * Mask windows warnings from third party libraries (Boost/Asio primarily, 100+ duplicate warnings)
 * Add missing NET_FILES source group for VS 2013 source explorer.
 * Fix misc relevant warnings reported by VS 12 2013.