majalan

Copperbox revision 3232.

I've reworked ImpulseMap, removing the InterimIM datatype.

I've added a module Trail for building proto ImpulseMaps, but Trail has monadic type so it can't fully replace InterimIM. Next I'll have to code some combinators that justify the introduction of Trial - for instance Trail should be building block for trills and tremolos (and should allow accelerating and decelerating onsets of trill notes).