Implement random shuffle
Implement BlockList::random_sample
Implement BlockList::to_matrices
Fix BlockList::drop
BlockList::random_drop
Test BlockList::drop functions
BlockList::random_drop single block
BlockList::random_block
Fix Matrix constructor; add possibility for optional cleanup
Tidy typo
Add BlockList::shallow_copy
Make BlockList::random_drop return the dropped element if exists after drop
Tidying
Sparse coding test: implement replenish() function
Implementing sparse coding test
Fix replenish()

Result coefficients are _not_ the random ones.

Result coefficients are the multiple of the random and
the original ones.
Matrix: implement pivoting
Extract working set gathering from replenish()
Original tests: use sparsity factor A
Tidying