Add a constant for the ID block used and replace it.
Clean up some comments and clarify expectations.
readBlock() did not properly halt tags after errors and the else
clause was superfluous. Properly handle error status.
Move currentActiveTags to be static and initialize it.
This allows for keeping track of max/current tags accross multiple instances.
The board has a second SPI bus wired up for communication with two RFID readers
if needed.
However, the code only provided a constructor with no arguments, preventing
the use of a second instance on the different bus.
Update the constructor and the definitions to allow changing the chip select
and SPI bus used when creating an RFID reader.
Add a new class to handle the RFID module and associated data
in order to track active tags.
Update main with RFID initialization and a minimal usage to
check it is working as expected.
