=htp refactor tuple join to foldLeft-based implementation, unify tuple operations
!htp #16101 improve basic directive infrastructure, add more scaladoc, fix smaller problems
=htp enable tests that were erroneously disabled due to specs2 -> scalatest copy-pasta
=htp small improvement to Marshaller
!htp #15935 clean up and extend unmarshalling infrastructure
+htp #15929 port ParameterDirectives from spray