Add 2 additional new optional relation types for committees

As requested by @scorbett, we will need to add 2 new relation types to cover all use cases of councils. In this case we will be adding a new RP relation suffix for planning council reps and PM for PMC representatives. These will apply to all councils, as it will reduce complexity in the implementation. So long as it isn't used or created, these will just be empty and won't clutter the data out.