Fix package installation problems and refactor classes

[Angelina-C]

The package version 1.0.0 from PyPi could not be installed. This was due to the code not being organized in a package. The following was done to fix the issue:

• Create a Python package adb_pywrapper (note the underscore, a dash will not work)
  

• move adb-pywrapper.py to this package
  

• move the contents of adb_init.py to the package init
  

• improve the setup.py to find the package
  

• refactor the contents of adb_pywrapper.py so the imports are clean
  

• adjust the README to match the correct imports