Cevallo should follow the style of other Algorithms

This will allow testing Cevallo with other encryption schemes
than ShamirPSS.
restructure code and introduce CryptoEngine

The algorithms are now split between at.archistar.crypto.secretsharing
and at.archistar.crypto.informationchecking. As it gets tedious to
configure the algorithms a new interface CryptoEngine was added. The
basic idea is that end-users are just instantiating a CryptoEngine and
the cryptoengines themselve configure all needed compontents (like
symmetric encryption algorithms, secret-sharing, rng,
information-checking, decoder). This resembles Spring a little bit.

Let's start with an RabinBenOrEngine and a CevalloEngine.