- Rename MainActivity to HomeActivity
- Move functions.kt one level up
- Rename package `extern` to `libraries`
- Fix layouts and layout elements (nomenclature:
`activity_fragment_element`)
- Move SectionsPagerAdapter code into the related activity kotlin file
+ Fix `top-margin` in the choose activity
+ Rename `ViewPager` files for Settings to contain the string 'Settings'
+ Rename `firstStartup` to `Tutorial`
+ Remove unused library imports in `SettingsActivity.kt`