[Not for merge] Android 4 compatibility

[di72nn]

Notice: minimum Android version requirement is not going to be lowered from Android 5 in the official app, but this branch can be built and used by those who need it.

I wanted to know which things are compatible with Android 4 and how hard it is to maintain compatibility.
Not worth it. So the remaining legacy version checks should be removed from master.

Tested on Android 4.0.3 emulator (API 15).

There's a security issue with JavaScript having access to any Java methods (not only specifically annotated to work with JS) on the injected into WebView objects on Android <4.2.

WebView: window.getSelection() seems to not work (maybe an emulator issue, though). Maybe workarounds are possible, haven't checked it. As a result:

• "Add tag" from selection doesn't work.
• Annotation creation doesn't work. Displaying, editing and deleting annotations works (to my surprise).

Full-text-search is enabled only since Android 4.1. Android 4.0 uses the old title-based search.

TTS: parsing seems to work, didn't check the work with TTS engines. Guaranteed degraded fast-forward/rewind functionality on Android <4.0.3.

This branch is updated with force-pushes. Backups of the previous versions: 2.4.2.

[di72nn]

Rebased on the latest release.

Linter fails and suggests to add android.defaultConfig.vectorDrawables.useSupportLibrary = true which satisfies it, but makes the app crash at runtime on Android 4.
As a result, ./gradlew build fails, but ./gradlew assemble assembles APKs (without performing checks) just fine.

[tristan-k]

I'm really looking forward to Android 4 compatibility because the Tolino Shine 3 only runs on Android 4.4.2.

[di72nn]

@tristan-k there's nothing to look forward to - this PR is not going to be merged. You can build the app from this branch yourself - just use gradle assemble.