Add a comment field to the user permission entity.

[chrisala]

The field could be optional.
The field should be editable on the MERIT user permissions table by FC_ADMINs only. (Read only for other roles or invisible?)
The user columns accepted by the project load should be renamed and populate an appropriate value in the comment field. e.g PRIMARY_ADMIN, SECONDARY_ADMIN_1, SECONDARY_ADMIN_2, PRIMARY_PM, SECONDARY_PM_1, SECONDARY_PM_2 should add a "Primary/Secondary" value to the comment field.