Move SQLAlchemy type definitions to separate module
Add composite uniqueness constraint to rdf statement tables on (s, p, o, context) tuples. Previously it was possible to have exact same triple inserted multiple times
Some cleanup and more Pythonic naming style around table creation and naming
Also:
Drop Python 2.6 from unit-test matrix - By now safe to say 2.6 is obsolete, this rids us of 4 test matrix rows (Python version X db engine backend) making CI cycles faster
Switch to use the more idiomatic logging.exception for reporting exceptions rather than sys.stderr prints
Remove all conditioning on own package version - this is definitely an anti-pattern, any component which wishes to adhere to a specific version of this package should use a strict version specifier for this package rather than us having to maintain all this conditional logic for backward compatibility! for database schema version issues the solution should be schema migration (e.g using Alembic)
WIP - Continued re-naming to more Pythonic naming convention across the board
Also: