jtag/drivers: add support for Nu-Link (Nuvoton ICE) over usb

Add support for Nu-Link1 over usb hidapi and config file.

The original work is fetched from Nuvoton github.
Code cleanup, fix merge conflicts, compile and runtime issues.
Switch the code from libusb to hidapi, being the device HID based.
Add documentation.
Merge fixes for multi-word memory read.

Reset is not fully compatible with openocd framework; currently
the target is reset and then halt at openocd start.

Change-Id: I9738de4e26783ba462ea3e39ec32069fd5bb7d94
Signed-off-by: Zale Yu <cyyu@nuvoton.com>
Signed-off-by: Saravanan Sekar <saravanan@linumiz.com>
Signed-off-by: Antonio Borneo <borneo.antonio@gmail.com>
Reviewed-on: http://openocd.zylin.com/5635
Tested-by: jenkins
Reviewed-by: Marc Schink <dev@zapb.de>

src/jtag/drivers/Makefile.am

@@ -143,6 +143,9 @@ endif
 if HLADAPTER_ICDI
 DRIVERFILES += %D%/ti_icdi_usb.c
 endif
+if HLADAPTER_NULINK
+DRIVERFILES += %D%/nulink_usb.c
+endif
 if RSHIM
 DRIVERFILES += %D%/rshim.c
 endif