Create *.Extra module and not reexport it by default

[chshersh]

• groupBy functions
• BoundedEnum

every      :: (Bounded a, Enum a) => [a]  -- all values
cycleSucc  :: (Bounded a, Enum a) => a -> a  -- like succ, but doesn't fail on maxBound
safeToEnum :: Enum a => Int -> Maybe a  -- Nothing if Int outside enum range

• Bifunctor

bimapF  :: (Functor f, Bifunctor p) => (a -> c) -> (b -> d) -> f (p a b) -> f (p c d)
firstF  :: ... similar
secondF :: ... similar