YAML Porting Issues

[mormj]

• atsc plinfo size on the port - sizeof(plinfo) in the code - yaml doesn't understand this, nor should it -- some sort of yaml constants?
• fir_filter blocks need 3 way templating
• file_sink_base inheritance with the pybind is funky
• can constants be included from a top level yaml file
• can constants be generated and python bound from yaml