Increase readability - printf splitted in multiple calls
Added a ! to the JLinkExe call to prevent the "make: Error 1 (ignored)"
See also → http://forum.segger.com/index.php?page=Thread&threadID=1545
Reduced printf verbosibility
Added make vars FLASH_BOOTLOADER_UICR and FLASH_SDK_BOOTLOADER_CONFIG
- You can FLASH_BOOTLOADER_UICR set in your project specific Makefile,
if your project is a bootloader.
  This causes the storage of the bootloader's address to UICR 10001014
so that it is called by the SoftDevice during bootup
- You can FLASH_BOOTLOADER_CONFIG set in your project specific Makefile,
if your project is a normal application and your target system consist
of a bootloader which is based on the Nordic Sdk.
  This causes a write of some configuration data into the last flash
block (typically 16 byte at 3FC00 for a 256k device) that notifies the
bootloader that there is a valid application in the flash.
Changed FLASH_BOOTLOADER_UICR / FLASH_SDK_BOOTLOADER_CONFIG to ifdef
Hack to suppress the block verification error when writing the uicr