Adjust password editing behavior

TODO item done in this commit (exported by TODO in Python):
  (TODO grabber) 031: [DONE] When showing pass edit view, check 'password.isUsed'.
  (TODO grabber) 032: [DONE] When showing pass edit view, if the cell is unset, focus on the text field.
  (TODO grabber) 034: [DONE] When showing pass edit view, animate its background color if pass cell is gray.
  (TODO grabber) 035: [DONE] Move 'backgroundColorOfPassword:' into CPPassword
  (TODO grabber) 036: [DONE] If password text is set to empty, mark it with not used.
  (TODO grabber) 037: [DONE] When hiding pass edit view, animate its background color if pass cell is gray.