Custom fields/flags for members in DB

[XertroV]

Allow custom fields and flags to be created in DB

Allow staff with a TBD role to create fields (with a jurisdiction attached) - marked as editable by members or not

All field values are Maybe as and a default can optionally be provided

Users can set values for these fields if they're editable - need to add UI for this

Non-editable fields can be populated algorithmically (e.g. determining a user's electorate)