CMake: change version handling

version are not only 3 numbers now.

we let `git describe` handle the version

on dev we will thus have :
v1.3.1-72-gff74aa0

and on release will only get the tag:
v1.3.1
Python: remove useless version number from packages

the version number is handled by debian packages, so we don't need this
Install: no need to change version number anymore

the version number is now the git tag, so we don't need to explicitly
change the version number
Merge pull request #675 from antoine-de/change_version_handling

Change version handling