Rename currently listed Water Management Districts to SJRWMD

[mradamcox]

We have Management Area Groups with names like "Water Management District - North" but in reality these are subsets of the overall St. John's River WMD. They need to be renamed with SJRWMD in place of Water Management District so that
Water Management District - North
becomes
SJRWMD - North

Renaming must take place in the following places:

• https://github.com/legiongis/fpan/blob/master/hms/management/commands/areas.py#L230
• https://github.com/legiongis/fpan/blob/master/hms/migrations/0005_migrate_legacy_areas.py#L23
• in the production db admin backend (rename objects directly)