Added InteractiveTipCalculatorActivity.java and +

1 ) Created and Added InteractiveTipCalculatorActivity.java
2 ) Created and Added interactive_tip_calculator_activity_layout.xml
3 ) Added quite a few references to constant String objects in
/res/values/strings.xml
4 ) Edited AndroidManifest.xml to create permissions and declare my
newest activity in the xml so that I could test it.
5 ) Edited NavigationActivity.java so I could create a Button object and
then aim an intent towards the newest Activity
6 ) Edited navigation_activity_layout.xml by declaring the Button I
mentioned in 5