Inline Intent helper methods

[veyndan]

Inline Intent.get___Extra(String) methods as:

• Logic needs to be duplicated between BaseFragment and BaseActivity to continue using this approach, reducing code maintainability.
• The helper methods in BaseFragment always uses the null permissible getActivity() when the logical flow may require the use of the non-null assertive requireActivity().
• Calling getIntent().get___Extra(String) is a pretty standard practice, and makes it known that the get___Extra(String) is being obtained by the intent that the started the activity.
• BaseActivity#getIntExtra(name: String) returns -1 if the extra name is absent. By covering this up in a layer of abstraction is a potential source of difficult to find bugs.

[Meisolsson]

Why do we use activity?.intent? in app/src/main/java/com/github/pockethub/android/ui/gist/GistFileFragment.kt but activity.intent in app/src/main/java/com/github/pockethub/android/ui/commit/CommitCompareListFragment.kt?

[veyndan]

In the original app/src/main/java/com/github/pockethub/android/ui/gist/GistFileFragment.kt we don't assert that the activity should be non-nullable, so I have kept the logic the same by using activity?. In the original app/src/main/java/com/github/pockethub/android/ui/commit/CommitCompareListFragment.kt we assert that activity should never be null, so in the later lines activity is never null. I haven't changed the nullability contract in this PR.

[Meisolsson]

Alright, that makes sense. I'll check this in a bit.