state: added strictLocalID()

Like localID but reports failure if the env UUID prefix for the State
wasn't present.
state: env UUID migration for relations collection
state: env UUID migration for the relationscopes collection
api/uniter: fixed ordering assumption in TestJoinedRelations

This test used to sort the received tags before comparing to the
expected results but a recent revision changed this. The test was only
passing by luck because the returned tags are ordered according to
MongoDB's default undefined ordering. The env UUID update for
relations changed the returned ordering making this test fail.

jc.SameContents is now used so the returned ordering is irrelevant.
Merge pull request #985 from mjs/relations-env-uuid

state: env UUID migrations for relations and relationscopes collections