Query latest Topic or Category. New Category Column in model

1. Changed the first alembic script so it'll work in both sqlite and postgresql
2. Added a category column to query the git/logger/fas/... category
3.  Wrote a second alembic script for the new column that can upgrade in postgres and sqlite but only downgrade in not-sqlite.
4. Added functionality to datanommer-latest so that you can now query the exact topic or per category