Begin user interface design

- Customize ViewPager tab names
- Correct MainActivity imports and extends
- Update AndroidManifest.xml with features and permissions
- Increase minSdkVersion for Android Beam NFC large files compatibility
- Delete unnecessary files
Begin Fragment design

- Fix code formatting with curly braces on their own line
- Add SenderFragment class
- Add ReceiverFragment class
- Add DocumentListFragment class
- Add model package
- Add Document class
Begin DocumentListAdapter class implementation
Fix fragment import type and variable name

- Change to using android.app.Fragment instead of
android.support.v4.Fragment
- Fix error in variable name use in DocumentListAdapter
- Add beginning of code to return actual Fragments in MainActivity
Add fragment XML layouts and fix crash
Implement basic UI and begin NFC code