Adds ballot_base class.

- Ballot item classes can extend ballot_base in order to reuse __construct() and save()
- tests cover base class methods
remove trace stmt
Resolution extends ballot base

- fix param type for resolution properties- set as PARAM_TEXT in form->definition(), page was expecting PARAM_ALPHA.
- update call to resolution constructor
GPL
update office class to use ballot_base; remove debug in ballot.php
update the param typing