Clarify license: GPLv3 or GPLv3+
Some files, for instance totalopenstation/models/trimble.py or totalopenstation/models/leica_tcr_1205.py, claim to be "Under the GNU GPL 3 License", which does not indicate later versions of the GPL are allowed as well. This is in contrast to files like totalopenstation/output/tops_sql.py, that clearly allow later versions. Please clarify the licensing issue.
Submitted by Volker Fröhlich.