Performs Flash initializations, which includes: Call all 'init' routines in units, in the right order. Order does matter, particularly when restarting from a checkpoint file. For the most part, Driver_initFlash calls another units' init routines directly, like call IO_init or call Grid_init. This routine also makes calls to other Driver initialization routines like Driver_initMaterialProperties or Driver_initSourceTerms. These routines then call the unit-specific initialization routines. This level of abstraction was added to simplify the initialization calls.