IDL43 — bitset mapping

All constructed types map to a C+11 class with accessors, but the new bitset mapping is an exception now, it delivers no accessor methods which gives a different API to the programmer. We propose to map to a class with accessors, similar like struct, or fastdds does in their implementation (see https://fast-dds.docs.eprosima.com/en/latest/fastddsgen/dataTypes/dataTypes.html#bitsets). Also the IDL inheritance is gone in C11, propose to use a derived class, so that in the C+11 code there is also an inheritance