Make it possible to create erlydtl beam files with full path in the name

if DTL_FULL_PATH=true
  /templates/a/b/c.dtl -> a_b_c_dtl.beam
otherwise (as it was before)
  -> c_dtl.beam

Update erlydtl.mk

add info about erlydtl compiling options in readme, fix formatting in erlydtl.mk, merge erlydtl.mk into erlang.mk