- Fix some issues and improve efficiency of some RunPython code in
migrations.
- Merge some migrations.
- To simplify, any RunPython don't get a revert function.
BDS + COF
The permissions assignation is triggered by the `post_migrate` signal since the
permission table will only be populated after the migrations have been applied.
Fill bds.models with the required fields; add migration scripts, and a stupid
unittests that checks the model really works.
Note: old fields will migrate to datetime.now().