Add support for two new password validators:

- Issue #338:  Prevent users from selecting a password that matches the value
  of any attribute (or a specified set of attributes) in that user's entry.

- Issue #341:  Prevent users from selecting a password that matches a value
  contained in a dictionary.

Both validators support both forward and reverse matching, and for the
dictionary password validator I have compiled a dictionary from public domain
word lists.