Merge pull request #407 from EmbeddedMan/master

Added support for all 6 serial ports on Microchip version of Fubarino SD...
Code added to fix issues #410, #409 variant variable in platforms.txt not added. Other boards need to overide this value to use their own custom variant.
Reverted commit #d29ceba1fb897c5a77029fdc2e81f4bd53eee65b for issue #402
For issue #402 changed the code per @majenkotech recommendation
Potential fix for issue $402 - as per majenkotech's dreamy suggestion, we're now telling the computer that we support "Set_Control_Line_State" communications.