Update packaging for Python 3
This PR updates the Debian and RHEL packaging for Python3 and closes #77 (closed) by separating off the scripts into their own package. The binary structure is now
- python3-dqsegdb: just the python3 library
- dqsegdb: the client scripts that depend on python3-dqsegdb
As a result this should be surprisingly backwards-compatible for downstream dependents.
I have a hunch the RHEL builds will fail because nobody provides pyRXP for Python 3.
EDIT: closes #76 (closed), closes #77 (closed).