Fixed flags
Closes #3 (closed), #24 (closed)
Moved IntegerRegister in register.py to its own file. Removed the Flag class and made the flags into integer registers instead. Made the L-flag be just a signal and put the "register" part in the loop counter instead (this is how it works in MIA).
Finally, added a rudimentary signal viewer class in the GUI to visualise the L-flag. Currently the signal viewer lacks functionality such sa locking itself in place and having its position saved to and loaded from a layout.