communicate with BS2 over serial, add output pane for data, clear data on download - closes #47, closes #48, closes #49

[phated]

What's this PR do?

Adds support for BS2 communication over serial and displays the data in an output pane positioned under the editor. It also clears the output pane before downloading to the BS2.

Where should the reviewer start?

Pull down the application and rebuild.

How should this be manually tested?

I've been using the following code snippet to test:

'{$STAMP BS2}
'{$PBASIC 2.5}

Counter VAR BYTE 'Counter for loop
FOR Counter = 1 to 20 'Loop 20 times
  DEBUG "A really long text string, does it buffer this?", CR
  PAUSE 250 'Pause 1/4 second
NEXT
STOP

Any background context you want to provide?

Nope.

What are the relevant tickets?

Closes #47
Closes #48
Closes #49

Screenshots (if appropriate)