Added some details to take in account STM32F411 properly

1. Updated README.md to integrate NUCLEOF411RE
2. Updated NUCLEOF411RE.py to correct some syntax and really get it build
3. Updated build_board_json.py to normalize path and get sys.append to work on ubuntu 14.04 LTS
4. Updated build_platform_config.py to setup the timer used with STM32F411 boards, so far it is now the same as for STM32F401RE
5. Stopped the auto removal of ending whites spaces but true on ending lines of files. (: