genlib: add CRCEngine and CRC32 example

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

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