Added commands

Commands are for users to do special things outside of just chatting.
Right now that's just emotes and nicknames. The commands now need to be
initialized at the beginning of execution. These commands are handled as
function pointers in a command structure that then gets attached to a
ptab for later retrieval.
Command parsing and a simpler sending functions

First we command parsing. No use in having commands if we can't
determine if we're looking at a command at all. This meant that we
needed to pull some functionality out of our send functions and put them
into the parsing. For instance, the output should be determined by the
function creating the buffer to send, rather than the send function
itself.
Changed the ptab structure _name_ to reflect what I did for command(_t).

The typedef remains the same