Add mechanism for temporarily increasing board size

This is an alternative to #53 which allows us to temporarily increase board size, without simply removing the limit. It requires a consideration of board size every year in which the desired size is more than 14.

Please click the Approve button to vote in favor of this change, which we can also discuss at tomorrow's meeting. This will require a 2/3 vote to be approved.

Vote deadline: one week from today: March 20.