Extend merge request !310

This changeset consists of 20 commits.

The first seven address issues discussed in merge request !310 (closed). These issues improve the UI changes for the NowPlayingBottomSheet. These changes are:

• 781152d0 - Suppress BottomSheet close on show.
• b2701a2a - Prevent BottomSheet tap leaking to nav panels.
• 4c1ba726 - Give notification tap action semantic meaning.
• d4f5fe1f - Show BottomSheet upon notification tap.
• f50c513d - Increase player controls touchpoint size.
• 08df4d4c - Persist BottomSheet open/close state.
• c1e4e891 - Remove redundant LinearLayout.

The next three commits fix crashes when switching between portrait and landscape views. The concern for these crashes were raised in this comment from !310 (closed). The crashes are further described in issue #145 (closed). These changes are:

• 752542fb - Do not create unnecessary Picasso objects.
• 2708f67a - Refactor CoverArt.withContext().
• 4ca60bec - Fix landscape view induced MainActivity leak.

The final ten commits clean up warnings reported by AndroidStudio. These are not stability or usability issues, but most stem from changes made in !310 (closed) and this merge request. These changes are:

• ba5574dd - Cleanup: remove unused imports.
• fabd78de - Cleanup: remove unused function.
• 8d69fcc1 - Cleanup: mark internal fields private.
• 3bbdd3f9 - Cleanup: minor tweaks suggested by AndroidStudio.
• 1b197626 - Cleanup: do not create unused field.
• 09b6a27e - Cleanup: Avoid shadowing "it" object.
• 8890e3c9 - Cleanup: "cascading if" -> "when".
• b263aa78 - Cleanup: use ContextCompat to load drawables.
• d949f9fe - Cleanup: SuppressLint adjustments.
• 96edf761 - hdasch/bottom-sheet-refinement Add a changelog entry.

With these changes, I believe !310 (closed) deserves review and further testing. It should be considered a merge candidate.