Cp admin simplified access updates

[caitlinroach-nhs]

Updates to make it so group admins can access individual pharmacies.

• Group admins can view the individual pharmacy by clicking a button on the individual pharmacy page in the admin interface.
• They switch back to the admin interface via the "Back to organisation" button next to the pharmacy name in the navigation
• Group admins cannot be added as individual pharmacy users -- if this is tried, there will be an error message.