tools (utils): better repository version handling:
- removed save_dir_path and .hg_data/pickle method: it is not needed to save repository data anymore as its version is now saved on installation by setuptools_scm
- added "distance" (number of commits since last tag)
- use twisted's which method to find the hg executable
- result is now cached on first execution
- fixed dirstate method
- at last resort, try to find the repository version using the package version, as it is saved there by setuptools_scm