Use lattice for LFOs, so they share clocks, and allow setting ppqn

[sixolet]

This suggestion does one of the things I reccommended:

• Uses lattice instead of a raw clock, so the LFOs can easily share a clock
• Allows the user to specify the ppqn per-LFO. Values that divide 96 evenly are going to be better, because they won't leave residual phase in the lattice, but other values are okay — they just won't bang quite exactly on the dot every time.
• I hope I have not been misusing the hook library, but it was useful.