Test all valid and invalid addressing modes for ADC.

All variants of the ADC instruction are tested and verified.

Fixes include:
* signalInvalidAddressMode() should only print error during the second
  pass.  Previously it was being displayed twice.  Once in the first
  pass and then again in the second pass.
* isAbsoluteOrZeropageIndirect() had a bug in the BASIC code where I
  referenced the CP$ variable instead of CP%.
Added error text message descriptions