Reordering the features to accomodate filterbanks.

It's not the same order as in Tosato's paper, but the order doesn't
(shouldn't) matter. It leads to a pivot of cov matrix rows and cols,
which shouldn't lead to a difference in distances.
rename w -> weight.
Generalize! Patches can be defined by config.
Move filterbank stuff from .h to .cpp

Mainly in order to avoid including opencv in the header of filtebank.
Refactoring foreach_img to common file for mains.
Some more refactoring of "main" code parts.
Model persistence.
Parallelization!