Config edit checks and visualizations

* Allow string lists ('admins', 'showLangs', 'whitelistedLangs', 'ips')
  to be entered as a string instead of an array - will convert automatically
* 'admins' will now check that the account actually exists
* 'admins' will now be shown as a comma separated list rather than boxes

Change-Id: I0a696ccb42fc52290f4cf39cddc2ae73fb47b477
Merge "Config edit checks and visualizations"