Improvements for CurieBLE library

[biagiom]

• Add some improvements to sketches of CurieBLE library : add the line while(!Serial) ; in order to wait for the Serial port to connect since Arduino/Genuino 101 has native USB port;
• Update the keyword.txt file of CurieBLE library;
• Improve BLEAttribute class of CurieBLE library

[eriknyquist]

You've changed many files from other libraries here besides BLE. Please remove these files, and add one PR per library.

[biagiom]

Hi @eriknyquist,
sorry for my mistake, I have split the changes over different pull requests :

• Improve CurieBLE library #284 adds some changes and improvements to CurieBLE library,
• Improve sketches of CurieIMU library #285 improves some sketches of CurieIMU library
• Improve sketches of CurieI2S library #286 improves some sketches of CurieI2S library
• Improve sketches of Wire library for Arduino/Genuino 101 #287 improves some sketches of Wire library
• Improve sketches of different libraries that use Serial communication #288 improve some sketches of different libraries . With this pull request I have grouped sketches from different libraries because this pull request has the main intent to improve sketches that use Serial communication over the virtual serial port through the Serial object
  (there are libraries for which I have improved only one sketch and so I thought it was better to group them together because I made the same changes in all the sketches of Improve sketches of different libraries that use Serial communication #288)

Best regards.