Add support for perturbation magnitude/direction

[giladmishne]

Modifies perturbation names to include an optional magnitude, separated from the gene name by *, i.e. p53*200, brca2*0. The magnitude is an integer, interpreted as a percentage change from base (i.e. 0 is a knockout), and is used to multiply the perturbation embedding. If no magnitude is provided, a default one of 100% is used (to be backward-compatible with the current implementation).

Many of the changes are trailing-whitespace removals from an auto-formatter; the only real modifications are parsing and storing an additional pert_magnitude array with the rest of the data and using it to modify the embedding.