Added new input methods and refactored 'view' command.
Added new input methods and refactored 'view' command.

* 'masked_read_line' behaves as 'read_line', but hides input.
* 'read_new_password' will ask and confirm a new password.
* Delegated optional entry lookup logic to 'get_active_entry'. Other commands,
  like 'edit', would have to re-implement the same logic.
* 'view' command uses 'get_active_entry'.

aaronbolyard/blobby