ristsender/ristreceiver --help-url has some invalid options advertised

When using --help-url with the ristsender/ristreceiver the following arguments are presented as valid but cause invalid parameter errors.

param verbose-level=# Disable -1; Error 3, Warning 4, Notice 5, Info 6, Debug 7, simulation/dry-run 100
param multiplex-mode=# Controls how rist payload is muxed/demuxed (-1=auto-detect, 0=rist/raw,  1=vrt_src_port, 2=ipv4)

• verbose-level is defined as RIST_URL_PARAM_VERBOSE_LEVEL but isn't used anywhere. When used by the ristsender/ristreceiver it will log this error.

Unknown or invalid parameter verbose-level

• multiplex-mode is suggested as a rist:// URL option in the help message but the usage of RIST_URL_PARAM_MULTIPLEX_MODE in rist-common.c indicates it is actually an udp:// URL option.