Fix inconsistent naming and docstring

(1) In the XML files, all keys except "log" are used as parameter names.
(2) Most files use the parameter name "log" to flip logging.
    So change the ones that use "logging" or "debug" to "log".
(3) packet_mod constructor does not have the argument payload_length.
(4) Add missing args to some docstrings
(5) Resolve inconsistency between gmsk_demod code and doc