Merge pull request NordicSemiconductor#170 from NordicSemiconductor/f…

…eature/retries

New feature: retrying DFU in case of undesired disconnection

Version 1.8.1

Version 1.8.0

Version 1.7.0

Version 1.6.1

Version 1.6.0

Version 1.5.2

Version 1.5.1

Version 1.5.0

Bug fix: Passing correct extended error number and message