Add MSP-EXP430FR2355

[rocketfuze]

Would like to request the addition of another launchpad board, the MSP-EXP430FR2355. The board has useful analog features as well as fram, and would make a good addition to the MSP430 launchpad lineup.

[argolomb]

I can't find any reference to this issue on platformio-core. What does we need to add a board?

[fpedd]

See my PR #28.