Add "hp" encoding

[olgabot]

HP encoding is yet another lossy encoding like Dayhoff (#689) that encodes the amino acids into a binary encoding as implemented here. Here's a little table:

Amino acid	Property	Dayhoff	Hydrophobic-polar (hp)
C	Sulfur polymerization	a	p
A, G, P, S, T	Small	b	A, G, P: h S,T: p
D, E, N, Q	Acid and amide	c	p
H, K, R	Basic	d	p
I, L, M, V	Hydrophobic	e	h
F, W, Y	Aromatic	f	h

[luizirber]

Implemented in #758