[ADD] Database cleanup module
[FIX] Typo, comment
[FIX] Remove unused import, add missing copyright notice
remove relations when purging models
avoid ''NoneType' object has no attribute 'exists'' error when purging models
[FIX] avoid ''NoneType' object has no attribute 'exists'' error when purging models
[IMP] Remove the fields having a relation to the purged models.
fix my change guewen.baconnier@camptocamp.com-20140203103254-v1mzu2uib047xb9h, wrong lines replaced...
[FIX] error in previous merge
[FIX] Don't remove uid field from wkf_instance, which is written in
    raw SQL query (but never read afterwards). Workaround for
    lp:1277899
[FIX] Preserve dangling workflow table which is in use
[RFR] Group models per table when detecting columns to purge
      to prevent problems with models sharing the same table
[ADD] Allow purging of dangling data entries
[FIX] Data purging now working
[IMP] Docstrings
[FIX] Label
[FIX] Catch attempt to unlink field from nonexisting model
[RFR] Flake8
[CHG] Migration to 8.0
Merge branch '8.0' of https://github.com/oca/server-tools into 8.0-add-database_cleanup
[CHG] database_cleanup: move description to README.rst