Monad/Applicative/Functor instances for Eff

So now you can use it in a Monad transformer if you really want to.
Add 'byReflection' tactic

Similar to 'applyTactic', but its argument is a reflection function
which builds a tactic by reflection on the goal.
Explain strange case in reflectListEffElem!
Merge branch 'master' of github.com:idris-lang/Idris-dev