Improved the variables transfer system
-Introduced a new variables transfer system, which does not need a
predefined variables list (previously in the Excel sheet), but works at
runtime. The list is built directly on the board during init, then the
computer can download it. The Excel document has been removed.
-Completely rewritten the MATLAB GUI, the displayed variables list is now
dynamic.
-Firmware: removed the "status register" that was unclear.