Replace library version system.

[jgalan]

Up to now we update the library version inside CMakeLists.txt manually. I think a more efficienct way would be to read the latest git tag name inside the cmake system so that just tagging is enough to define a human version.

What do you think?

the cmake variable LIBRARY_VERSION inside cmake could be simply filled by a call to a git command that returns the latest tag.

[jgalan]

I have already implemented a preliminary here: rest-for-physics/rawlib@608d4f3 and here rest-for-physics/rawlib#110

[lobis]

I was already working on this also, I have it almost finished, submitting the PR in a few minutes.