sequenceserver: inform users if an invalid subcommand was provided (#17)
sequenceserver: inform users if an invalid subcommand was provided (#17)

Previously, SequenceServer would just ignore the subcommand and launch as if
nothing had happened. But it would raise an error if an invalid option was
passed. So it is only natural to inform the user if SequenceServer doesn't
recognize the given subcommand either.

Suggested-by: Ben J Woodcroft <gmail.com after donttrustben>
Signed-off-by: Anurag Priyam <6e6ab5ea9cb59fe7c35d2a1fc74443577eb60635@gmail.com>

vivekiitkgp/sequenceserver,jasminZ/sequenceserver,yeban/sequenceserver,yeban/sequenceserver,elsiklab/sequenceserver,vivekiitkgp/sequenceserver,jasminZ/sequenceserver,elsiklab/sequenceserver,aldermossy/sequenceserver,yeban/sequenceserver,yeban/sequenceserver,elsiklab/sequenceserver,lepbase/lepbase-sequenceserver,lepbase/lepbase-sequenceserver,vivekiitkgp/sequenceserver,deepakunni3/sequenceserver,aldermossy/sequenceserver,IsmailM/sequenceserver,deepakunni3/sequenceserver,aldermossy/sequenceserver,aldermossy/sequenceserver,lepbase/lepbase-sequenceserver,deepakunni3/sequenceserver,jasminZ/sequenceserver,IsmailM/sequenceserver,IsmailM/sequenceserver