[Fluxus] fluxa commits

[dave]

Hi all,

Partly as fluxus is now updated, I decided to use it (and scheme bricks)
for an upcoming algorave performance, so I've been fiddling with fluxa
again.

I've added the tb303 filter from Open303
(https://github.com/maddanio/open303) called "tb" (which is much much
better than the "mooglp/bp/hp" ones) and started work on an additive
node ("addit") for doing cheap and cheerful chord progressions...

I'm also wondering whether fluxa should be split from the fluxus code
base to it's own repo, partly as it has more build targets (e.g.
Raspberry Pi) than fluxus does, and it's also quite large generally.

cheers,

dave