Fix memcpy SegFault and GridControllerAccess

memcpy bytesToCopy argument was changed to sizeof(destination), which is always safe.
completely removed 'bytes' from Message Header

because implementation like enum { bytes=sizeof(MessageHeader) } will result in incomplete type error message
argument fix in initGrids call

somehow the order of localGrid and globalGrid arguments was changed
in Environment.initGrid vs. Subgrid.init, meaning initGrid crossforwards
it's arguments to init, which I find not beautiful and resulted in an
assert error:
   picongpu/src/libPMacc/include/mappings/simulation/SubGrid.hpp:50:
    PMacc::SimulationBox<DIM>::SimulationBox(const Size&, const Size&,
    const Size&) [with unsigned int DIM = 2u, PMacc::SimulationBox<DIM>
    ::Size = PMacc::DataSpace<2u>]: Assertion `localSize[i] <=
    globalSize[i]' failed.
Merge pull request #295 from mxmlnkn/fix-gol

Fix memcpy SegFault and GridControllerAccess