Visual Studio 2015 support

[riza]

To support to Visual Studio 2015 (VS 2015), this ticket will introduce these files:

- Solution file : pjproject-vs14.sln
- Project files : *.vcxproj
- Project properties sheet files : *.props

Please note that in VS 2015, VC++ directories settings are available in the user property sheet.

To include them in a global setting, use Microsoft.cpp.<Platform>.users (e.g: Microsoft.Cpp.Win32.user) properties sheet file.