- Implemented bin_op(): Nor sure if "constants.add(value);" are correct -> marked as TODO's
- Implemented generatePrintOperation() and included Method in Parser.java
- changed stackAddressOfAccumulatorValue to emptyAccumulator (boolean) (true -> acc empty, false -> acc points to top of the stack)
- inserted TODO in generateReadOperation()
	not sure, what to do if the accumulator is not empty -> save as auxiliary variable?
- corrected wrong condition in Main.java