First draft OSC patterns

[hryx]

Let's decide on an OSC pattern format for Moidpulate OSC and implement it. Here's a first stab.

---- global
/modipulate/quit
/modipulate/set_volume (float)vol
---- per-song
/modipulate/song/load (string)filename (int)id
/modipulate/song/<id>/unload
/modipulate/song/<id>/play
/modipulate/song/<id>/pause
/modipulate/song/<id>/set_volume (float)vol
/modipulate/song/<id>/set_tempo (int)tempo
---- per-channel
/modipulate/song/<id>/channel/<ch>/set_volume
/modipulate/song/<id>/channel/<ch>/vol_cmd (int)cmd (int)val
/modipulate/song/<id>/channel/<ch>/fx_cmd (int)cmd (int)val
/modipulate/song/<id>/channel/<ch>/play_sample (int)samp

To think about later: execute pattern jumps and other FX commands on-demand (scheduled).

[hryx]

Unfortunately, while oscpkt is capable of detecting pattern matching characters like [0-9] in an address pattern, it can't extract them.

I think my original proposal is more sexier, but for now we'll have to specify that the messages pass song IDs, channel numbers, etc. as arguments (reflected in #79):

/modipulate/song/set_volume (i)song_id (f)volume
/modipulate/song/channel/fx_cmd (i)song_id (i)channel (i)command (i)value

How C-like. 🍴 Anyway, I'll call this closed since this style seems to work for now.