cmsis-dap: add initial cmsis-dap support

cmsis-dap: add initial cmsis-dap support

This is based on work from:
https://github.com/TheShed/OpenOCD-CMSIS-DAP/tree/cmsis-dap

Main changes include moving over to using HIDAPI rather than libusb-1.0
and cleaning up to merge into master. Support for reset using srst has
also been added.

It has been tested on all the mbed boards as well as the Freedom board
from Freescale. These boards only implement SWD mode, however JTAG mode
has been tested with a Keil ULINK2 and a stm32 target - but requires a lot
more work.

Change-Id: I96d5ee1993bc9c0526219ab754c5aad3b55d812d
Signed-off-by: Spencer Oliver <spen@spen-soft.co.uk>
Signed-off-by: Andrey Yurovsky <yurovsky@gmail.com>
Reviewed-on: http://openocd.zylin.com/1542
Tested-by: jenkins