contributes to #11. Added a switch to select a given assembly as big or little endian (I assume a whole PLC will be one or the other, but individual data items will not switch back and forth). Implemented efficiently at runtime using a reverse 1D array and, during init, simply provide different indices to handle the array reversal (if little endian, index = assm size - data size - normal start index). This commit also includes updates tests (still manual).