take RAW_BYTES string out of bx_param_string_c into new param type bx_param_bytestring_c (better name, anybody?)
this is intermediate step, later it would be better to merge bx_param_string into generic template bx_param<type>
but bx_param_bytestring_cis not matching that concept (or probably will continue to inherit from bx_param<string>)
e8d0e718f1