Add multi-user support

[lfoppiano]

We should add the support to have multiple users working on the data without having to agree in advance who's working on what.
For example when one user click on "edit", the system might lock the record for a determined amount of time. If the record is not saved in 5 minutes, then the lock is released.

[lfoppiano]

A simpler solution could be as follow:

• 3 roles:

  • administrators (see everything and can assign documents to curators)
  • curators (can correct documents they are assigned, can see everything)
  • unauthenticated users (can only see what is visibile)

• Tasks (roughly):

  • add authentication page
  • add additional administraiton page to assign documents to users
  • add view for unauthenticated users
  • when a user is a curators will be able to edit only what it was assigned

[lfoppiano]

Out of scope, we use a script to allocate documents using URLs.
The script can also generate URLs for validation to a different curator