Appointer user role

[inghamn]

Currently, the only users directly associated with boards are the liaisons. The problem is that the liaisons do not make decisions on appointments. Most seats are filled by "Appointers", which currently are not represented as a user in OnBoard.

We probably need to evolve the current "Appointers" into a groups that can be assigned users such that we can notify individual staff members about things like vacancies and new applicants to boards.

[inghamn]

#352