genlib: add CRCEngine and CRC32 example

CRCEngine implement an generic optimized CRC LFSR and will generation of CRC generators and checkers.
CRC32 is an implementation of IEEE 802.3 CRC using CRCEngine.
actorlib/structuring: add Converter

Converter will allow easy conversion of data width on dataflows. It handles the 3 possibles
cases: downconverter, upconverter and direct connexion when data width are identical.
add packet support to flow/actor, actorlib/structuring