Add support for redirecting other serial streams

[nickmertin]

Expected Behavior:

User is able to read/write on any stream that can be opened between the brain and computer.

Actual Behavior:

User can only read on /ser/sout and /ser/serr, and can only write on /ser/sinp.

Additional Information

Suggestions:

• flags --istream <stream> and --ostream <stream1>[,<stream2>[,...]] to override the default of sinp and sout,serr
• flags such as --istream-bind <stream> <file>, which would act as a pipe from /ser/<stream> on the brain to <file> on the host computer, without overriding the default terminal streams; this could allow the user take advantage of other streams for data without impacting normal use of the terminal
• flag --stream-port <stream>:<port>, which would expose /ser/<stream> as TCP port <port>, in a similar way to -L in OpenSSH