v1.0: TR-909 kit (stable)

The first model909 release: the six Model:Cycles machines become a TR-909 kit (circuit-modelled BD, SD, toms, rim and clap; hats and cymbals from four WAVs you supply). This is the stable, 909-only version; build steps are in its README.

The TR-808 and TR-606 voices are on main, which is experimental.