UI for creating a batch of users from CSV
Refactor batch invitation code
Add DelayedJob for processing batch invites
Create models for storing batch invitation data

We are limited in the size of params passed to the DelayedJob job, so we have
to store them elsewhere.
Start to change to process in the background
Enqueue a job to batch create users
Basic page to show state of batch user create
A real file needs to be read before CSV.parse

The tests worked, but trying it in a browser errored.
Use the correct names for the form/fields
Translate faux signin permission
Save the correct data structure
BatchInvitations belong to a user

We need to know the user performing the invitation so that we can use
their role for the mass assignment of permissions. It also seems like
a good thing to record.
Add basic implementation of batch user create
Record invitation outcomes against batch users
Link to recent batches on batch create page
Show nicer feedback for batch user create
UX improvements
Deduplicate permission UI code
Only show 'synced' column for existing users

It's not useful for users that haven't been saved yet - they can't have a
synced status.
Gracefully handle no file being selected

The parameter was missing if no file was selected, so we got a nil pointer
error.