Versioning in Global source file

[stuart23]

File src/OpenFOAM/global/global.C has the following comment:

This file has the extension .Cver to trigger a Makefile rule that converts
'VERSION_STRING' and 'BUILD_STRING' into the appropriate strings.

We need to build the version number into the code somehow

[stuart23]

Build version MUST be hard coded so that it stays in the git and not just a cmake option. Consider this option: http://brianmilco.blogspot.co.uk/2012/11/cmake-automatically-use-git-tags-as.html