prettified output of parsemes
inlining phase 1 working

 - inlining of function-calls for a single depth works
 - multiple depths (i.e: add(sub(x, y), z)) does not work, as
   statements are not generated at correct locations
updates to parsing::algorithm

 - added id_equals_t
 - added passthrough
 - transform_depth_first now takes a down-fn and an up-fn
refactoring inlining for prefix depth traversal