Moved inheritance of cNumberGenerator from cAsyncModule to cSimpleModule
We are about to eliminate the need for special cAsyncModule objects
since it is more convenient to just stick to cSimpleModule in the
model implementation and active Horizon through omnetpp.ini switches.
Therefore, we first shifted the inheritance of cNumberGenerator from
cAsyncModule to cSimpleModule. This means that everytime you call
number generator functions inside a module, a local number generator
of the calling module is used rather than the one global RNG.