Create block for simpleterm_open() and simpleterm_close()

[dlcarrier]

Some hardware combinations on the Propeller Activity Board WX require disabling the debug port that Simple-Libraries automatically opens on P30/P31. This is done with a simpleterm_open() call and undone with a simpleterm_close() call.

There aren't currently any blocks for making the calls, so it is difficult to use BlocklyProp with a some hardware setups on a Propeller Activity Board WX, especially when using the WX socket with an XBee module.

Please create a way to make those calls in BlocklyProp. It could be a single block, with a drop-down menu to chose between opening and closing the port.

Andy recommended creating a drop-down menu that defaults to 'open', so that if someone accidentally includes the block, and doesn't modify it, there will be no effect for most users.