Adding users pages and logic back to CP admin interface

[caitlinroach-nhs]

In this bit of work we are adding back the users section and finishing up any final designs for that. This includes:

• Add users page to CP Admin interface
• When users are deactivated from a pharmacy, remove that pharmacy from their user page list.
• If the user is removed from the last pharmacy in their list, remove them from the users list
• add success messages for deactivation actions
• add ability to deactivate group admins (unless only one exists)
• additional variations of welcome emails for group admins and users who are added to multiple pharmacies
• add search for longer lists (more than 10 in a list)