112x semianalytical gradient

[amarini]

Simply port #690. Status as documented there.

I may use it to debug stuff atm.

[amarini]

First code to include CMSHistSum as well for rateParam and (symm) logNormals.
At the moment, the logic is to touch the other classes the least as possible.
The competitive thing, will happen if we compute and store the different component in the classes that use it (and vectorize it and cache it).