CryptKeeper improvements

- Status text was used enough to warrant it being a field variable
  instead of looking for the view every time

- Display proper text after changing pattern sizes (to input a pattern,
  not a password)

- Disable changing pattern sizes while validaing pattern

REFS: LETTUCE-557, LETTUCE-352
Change-Id: Ib4ecf04a58da8d1648d514d9650d69c33d9587a7
Signed-off-by: Roman Birg <roman@cyngn.com>