split transformer stuff into two classes
drop IS_GENERATOR flag after generator transformation
transformers are specified through command sequence
report transformer initialization error
[bugfix] dont evaluate direactly indexOf result as boolean
resolve transformer dependencies
obsolete old transformation flags
emitter is no longer used in tranformer
delay transformer construction
insert assert statement
move utility functions to _Util class
dependencies are not global
implement transformers as commands
no numbering to $generator and $return
update comments
dont use cpsTransformer inside callback
dont use callback to convert yield statements
remove unused parameter