Mapper.sc: updated prCallAction to propagate the instanceid

since it's now getting passed in from Mapper::Signal::input_handler()
Mapper.sc: fixed removeInput and removeOutput functions

to be able to actually detect the signal object from the name

had the keyword var where I should have had arg, and so the input
argument wasn't actually seeing the input to the function
added an example file to demonstrate libmapper-sc usage