Allow "day tokens" for privileges

[JarrettR]

Scenarios:

• Non-keyholder needs to get physical access to the space to help install critical infrastructure.
• Laser cutter repairman needs to test the system
• Local business owner donates obscene amounts of money to do a rush 3D printing job

Admins should be able generate a random PIN that unlocks a given privilege for, say, 24 hours. Or a scheduled time. Or a single login. Something, anyway.

[laftho]

I've added the GenerateTemporaryPin service. Requires gen-temp-pin or administrator privilege. You can only assign privileges to the pin you have. There is no UI for this yet. Partial support on the profile page (it will correctly handle multiple PINs)

When you gen a temp pin, it will be added to your own user profile and you are the owner of that PIN. Hence if you gen a PIN for someone, it will look as though they logged in as YOU. YOU are responsible for the PINs you generate and hand out.

Profile page needs to be updated to show the expiry dates, etc more visibly and indicate when a pin is expired and allow you to delete them.