Re-wrap and re-indent for readability and consistency
Use hash slice assignment instead of loop
Swap local_relname and remote_relname around in RelBuilder

All the other remote/local names refer to things _on_ the respective
tables, except these, which referred to the name of the rel _to_ the
named table. Fixing this longstanding inconsistency makes the code
easier to understand (IMHO, at least).
Swap order of _relnames_and_method return values

It makes more sense to have the local relname first, then the remote
relname and method. Note that this plus the previous commit are not a
no-op, since the meanings of the names have changed.