simplified Linker
updates to types and init_builder

* types are modified to the make interaction more clear and remove
  some potential to accidentally make global chages to types maps.
* init_builder wasn't really necessary anymore since handlers are
  being instantiated on every build now.
shuffle Builder and Linker into one file
fix typo
Writer

* modified Builder to make it require that transforms return generators
  which allows transformers to yield multiple objects
* basic Writer and handlers draft