git version determination w/o using CMake regex instead of sed

- offers better compatability to windows systems where sed is not present by default
- based on psi46/pxar@a4021b06b476ab16d9c1f297e3fdc85cc9a2a7a5
- addresses issue eudaq/eudaq#24
Merge branch 'master' of https://github.com/eudaq/eudaq