Add/improve errors for `.localAccess()` calls to non-local elements

[bradcray]

Notes to self:

• uncovered some issues with the implementation approach here, such as that Block and Cyclic's localSubdomains() weren't ever implemented for the case where they support oversubscription. I've fixed that, though haven't pushed it back up yet
• StencilDist is going to cause a problem here because of the use of localSubdomains, as that routine only returns the unique elements owned by the locale, not the fluff (which is arguably appropriate since the fluff is a cache and designed at present for read-only). So, how to handle that… move away from using localSubdomains? Special-case StencilDist?
  • Will PrivateDist and ReplicatedDist have similar issues?