Creating a new extension project (library) 
  - finished version is located in extras folder as a .rar file
  - new Android project created, min api 14 target api 21 (or 20)
  - "mark this project as a library" <- to make it a library in the
creation wizard
  - don't create a main activity
  - add a reference to air-interfaces.jar from the extras folder
(important, in the Order and Export tab, DO NOT export this .jar.
Classes are already defined in the DiscountLocator project, otherwise
you will have double .dex (dalvik executable) files with definition of
same classes which will break the project - however if it happens,
remove the .jar, clean the project and add it again without export)
  - in this new project add a reference to google-play-services_lib
  - add a layout for maps
  - add classes MapsFragment and Position
	- MapsFragment implements interface for OnDataChangedListener so it can
get store data and also NavigationItem interface so it can be added to
the NavigationDrawer
 Back to DiscountLocator
  - Handle references:
  1. remove google-play-services_lib from DiscountLocator
  2. add google-play-services_lib to Maps library project
  3. add Maps as a reference library project of DiscountLocator (now it
includes the google-play-services_lib)
  - now, you can add the map extension to your application with several
lines of code
  1. add permissions and KEY to AndroidManifest of the DiscountLocator
  2. add 5 lines of code to extend the application with maps