Collections don't have share ids and room keys.
Start converting PubSharesPassManager to a new scheme, to account for the
fact that the accountModel may have been restored from serialized state.

- we can't depend on pubSharesPasswords.loggedInTo() being called, so ditch
  that, and instead use a new "pubSharesPasswords" model setting, which may
  be resurrected from serialiation.
- don't store the current account name as state in the pubSharesPassManager
  object.  Instead, inquire of the accountModel object for the current
  account.

There is much further to go, including probably using settings to preserve
the passwords, if we want to retain this feature.
Whoops - pasted something incorrectly when restoring some old stuff.
Don't save the protected pubshare passwords with the accountModel
serialization.