Changed how LegalEntities are stored.

LegalEntities are now stored in a single Doxi/LegalEntities document,
which lets the entire list be loaded at once instead of needing to query
for all entities.
Added concurrency checking to EditEntitiesForm.

Instead of adding an Etag to the LegalEntities class, the form is
relying on the single session used, and setting
Advanced.UseOptimisticConcurrency = true.
Renamed EntitiesForm to LegalEntitiesForm.

Also updated references on the form to say "Legal Entities"
Changed how Departments are stored.

Departments are now stored in a single Doxi/Departments document,
letting the entire list be loaded instead of needing to query.
EditDocumentsForm was also updated for concurrency checking.
Added concurrency checking to EditSystemSettingsForm.