Adds some new nodes

[JakeCoxon]

• Aliases lt, lte, gt, gte
• Add neq node that does 1-eq(a,b). Could add a proper node here?
• Add sign node that returns -1, 0, 1 for a given signal
• Add clamp node that forwards to min,max
• Adds counter2 node that counts the number of rising edges until a reset signal is received
• Adds midi2frequency and frequency2midi. its helpful for the frontend to work in semitones in linear scale and then convert to frequency later, and midi notes are a good convention

Any thoughts or changes please let me know