Merge tag 'sparks-1.11.1' into develop

1.11.1
Enhancements (in fact: implementation) for `dev_postgresql()` fabric target.
Django/Fabric: pull in PG system development packages for automatic installation of python requirements.
bump version in setup.py
Merge branch 'release/1.11.2'
Merge tag 'sparks-1.11.2' into develop

1.11.2
Fix relative imports.
bump version in setup.py
Merge branch 'release/1.11.3'