[platform][lpc15xx] first stab at lpc15xx platform and target

Port to lpcexpresso 1549 board.
Builds, but not tested.
[platform][lpc15xx] import of lpcopen driver library

Version 2.08 of the library for lpc15xx
[platform][lpc15xx] add script and code to sign lk.bin

LPC wants you to stuff a checksum in the 8th vector slot.
[target][lpcexpresso1549] added target init code from lpcopen example code

Initialize the board and move some of the uart initialization into platform space.
[platform][lpc15xx] add irq vector table
[platform][lpc15xx] have the debug uart routine be interrupt driven on rx path