[CMake] Enhanced version management for the command "project"

[SF Markus Elfring]

Hello,

CMake provides an interface for the specification of version information
by the command "project".
http://www.cmake.org/cmake/help/v3.3/command/project.html

I find that there is a growing need to extend it.

1. How do you think about to preserve a software release tag there?

2. Software packages can often evolve and deviate from the specified version
   numbers after the moment they were copied to an useful location.
   Would you like to distinguish the extensions to a base version
   by any additional data (like a commit hash or revision identifier)
   from a content management system?

Regards,
Markus