WC-2627: mkdeb.sh: Tweak package builds
WC-2627: mkdeb.sh: Tweak package builds

- Remove `pandas` from the requirements, make it a "suggested" package
  instead.
- Base the version string off the git tag instead of whatever is in the
  package.
- Add `dh-python` to build-depends as per suggestions from the Debian
  build system.

vrtsystems/pyhaystack