added option for account deletion requests

[sheldor1510]

• Gave user option to request account deletion (only if user is not in any PI groups)
  
• Adds them to a new SQL table - account_deletion_requests
• Sends email to admins
  
• Updates user management for admins (graying and italicizing the users who have requested account deletion)
  
• [Enhancement] Allow user requested account deletion #43

[hakasapl]

Looks really good, just 2 things.

Could you make the "Request Account Deletion" form not be visible on the account settings page if the user is in a PI group? Instead, just print some text there that says something along the lines of "You cannot request to delete your account while you are in a PI group". This way you don't have to include the javascript alert with the error later.

Also, once the user requests account deletion, they should not be allowed to join or request a PI group. Those checks should happen in UnityUser/UnityGroup, but also in the frontend:

• The "Request PI Account" should be disabled on the account.php page
• The "+" button on the "My PIs" page should be disabled
• Both disabled buttons should have a note below them indicating that they are disabled because you have requested account deletion.

Let me know if I can clarify any of this, and thanks for this!

[hakasapl]

This should still check if the user is a member of any PI group before doing this. If they are, you can just die() the page, since it's not a state that should be reachable. Frontend verification is ideal, but the backend needs to verify as well since the user can change the frontend and submit the form in a way that you weren't expecting.

[hakasapl]

Thanks!