Also adds item/proc/BlockInteraction. Carries out common or configurable
checks for whether a given interaction should be allowed to continue;
reduces boilerplate somewhat.
Also refactors stamps to make this possible. Stamps are now configured
with authority_name and authority_suffix rather than setting the stamp
name directly. This is so that envelope seals can be sealed by a `Sol
Government seal` rather than `Sol Government logo stamp seal`, or a
`clown seal` rather than a `clown's rubber stamp seal`. You get the idea.
Also partially refactors folders. Their attackby behavior was a sin.
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