Extract core of perty function composition into separate bling package

o Improves error handling
  o Uses total functions to Option to be more aware of error situations
  o Inline with concrete docGens instead of weird outer wrapper
    (error handling is a docGen local concern with a sane default)
o Replaces all of docbuilders and docgenerator types with new DocGen[-T]
o Temporarily disables Pretty, ast support
o Rename HasDocFormatter => DocFormatting
o Rename HasDocGen => DocHandler
o Prepares ast printing to use converter pattern (not hooked in)