Proposed updates to ArduinoLadder

The following proposed updates are intended to develop improved integration between the ArduinoLadder GUI and the plcLib Arduino library.

1: Updated pulseTimer (new) / cycleTimer (modified) commands
2: Added Set and Reset latched output types
3: Modified timer commands to report time periods in milliseconds
4: Added analogue comparator commands (compareLT and compareGT) as
variants of the input contact.
5: Added Examples folder containing several folders of ladder diagrams
(with a .plc file extension).
6: Increased default number of rows to 50 (temporary fix due to maximum
examples size)
7: Added output pin names to list of inputs, to allow feedback
connections in examples. e.g Latches from discrete components (temporary
fix - perhaps an 'Allow feedback connections' checkbox could be
provided?