Missing "-p" in gl_server usage text

[mikini]

When experimenting with the issue in #37 I was puzzled that gl_server didn't respect port number on the command line as instructed by the usage/help text which indicated it should be 4th argument .

~/openpixelcontrol$ bin/gl_server --help
Usage: bin/gl_server <options> -l <filename.json> [<port>]
miki@vcas-miki2:~/openpixelcontrol$ bin/gl_server -l layouts/freespace.json 7890
Loaded "layouts/freespace.json" as channel 1 (625 shapes)
OPC: Listening on port 21984

Inspecting the source revealed that a "-p" is expected, so the help text should be something like (there are only l and p options);

Usage: bin/gl_server -l <filename.json> [-p <port>]

Also it would be courteous to indicate an unknown/unused option on the command line instead of ignoring it completely as is the case currently.