Allow modifying certain flags per town role, rather than being binary

[Xelarender]

Would be great in addition to the Public access options, to also have a Members Only option for Build, Container, Farm, and Interact Access. This would allow players to make their entire Town, Farm plots, or certain plots of land, accessible to all Town Members, without it being fully public to out-of-towners.

[WiIIiam278]

So this is half-possible now that you can customise flags (v5.5). Needed to implement this would effectively be a way of fine-tuning flag rights per role (currently, only privileges are per-role, with flags being binary on/off affairs). Adding this would be complex and likely require a significant UI design. Probably a low priority request for these reasons, as I do generally think the current system works well enough. Perhaps more usefully (and easier to implement in a satisfying way), adding a way of customising the claim types on the admin-side could be added.