Adding hideSoftKeyboard functionality  for android, updating package.json and updating ...

- Adding hiding soft keyboard for android. It checks whether soft keyboard is present using `adb dumpsys input_method` , if true hides keyboard using back button else throws an error.
- Updated package.json and submodule/appium-adb to new version of appium-adb
- Issue #2021
we put one space after `//` before the comment text