IP Block - Get output shape - Two different functions for similar purpose

Created by: laurentes

I've just noticed that there are two different functions for similar purpose in the IP block decomposition code. To get the expected number of blocks given an input array and some parameters, both getBlockShape() and getNBlocks() could be used. For the next release, we should remove one of them and update the bits which rely on these functions accordingly (at the C++ level, DCTFeatures and LBPHSFeatures).