Refactored to BigInteger, parallelization, shared memory

[lonevetad]

Signed-off-by: Marco Ottina [email protected]

Description

• the RPP's function parameter (the "registers") is now an array of BigInteger (it was of int)
• better memory management, as my thesis shows: the array mentioned above is shared on parallel computation
• the RPP interface now offers two methods, in order to implement the previous point and keep some retrocompatibility

[lonevetad]

I'll manage to perform a rebase onto develop and resolove merge conflicts by myself, in order to lower the Reviewer work