Speed up unit creation

[franck-boullier]

This removes unnecessary indexes in the dedup tables.

[franck-boullier]

Implemented and tested in the DEV/Staging. No issues.

[franck-boullier]

Implemented in the DEMO. No errors.

To do: after https://github.com/unee-t/frontend/releases/tag/beta-2019-06-12 is successfully deployed:
1- mass de-assign a user from many units.
2- mass re-assign a user to many units
3- check that user can still access the cases for these unit.

4- Run the automated UIlicious tests

If no error, then we can roll out in the PROD environment.

[franck-boullier]

Implemented in the PROD environment. No errors.
To Do:

• update the seed scripts
• merge this PR