Revert "Workaround for GHC #2247 being fixed. This lets us enjoy the inference benefits of the old semantics regardless."

This reverts commit 2db9d18f8ad89da8459c703e8f3b2863ad9c7f13.
Revert "Simplified (0 :: Int) to 0"

This reverts commit 582c67c38e1ec795ad2aaeafe226327ae30ab1f4.
Revert "More instances that are now possible"

This reverts commit d4cfb0e620c6b64b4d28e3eafd9b55a743173d48.
Revert "Using the new Indexable definition we can strip many explicit signatures from indexed types."

This reverts commit b3c7e2344d0e47715e02de7465b7f0e4433b6295.
Revert "Functional dependencies determine _instances_, not types!" -- except in HEAD

This reverts commit c9466d3f9fa9aa0a72f062437ade9bb830d0591a.