[Enhancement] Allow user requested account deletion

[bryank-cs]

It'd be helpful if a user could request their account be deleted with a button on the Account Settings page that emails the admins that they would like their account removed. It should be required that they have left all PI groups first, more for communications with the PI then any technical reason.

[hakasapl]

In addition to emailing admins, this should be stored in a new mysql table, user should have the option to request deletion of their account from account settings, which sends email to admins, and stores that info in the sql table. On the user management page that user should be a gray font face