Resolves Gradle deprecation and language version warnings
```gradle
Java compiler version 21 has deprecated support for compiling with source/target version 8.
```
The `java.toolchain.languageVersion` syntax is a superset that covers the previous syntax `android.compileOptions`
While Android Studio Gradle plugin should automatically use a default version of build tools, we can specify it:
https://developer.android.com/studio/releases/build-tools
Attempting to resolve lint exceptions on the build agent.
Fixes#2989
This updates the minimum supported Android SDK to 21 (Lollipop). This applies to KMEA, KMAPro, Sample Apps, KeyboardHarness, and FV Android app.
Tests/keyCode doesn't use KMEA so no change there.
#2640 fixed the FirstVoices OEM app from crashing on Android 5.0 devices.
This applies the same fix (updating to `androidx.appcompat:appcompat:1.2.0-alpha02`) for all the other Android apps.
* Also fix up history.md entries
Android Studio is warning a call (from Firebase) will be deprecated end of 2019. This updates the versions of
* Frebase
* Gradle from 4.10.1 to 5.1.1
Also stubs a missing keyboard event handler in some of the sample/test projects.
Fixes#750
Currently, Keyman for Android targets SDK version 25 (Nougat).
This PR targets the latest Android API and updates all the Gradle dependencies to the latest. This will remove some lint Obsolete warnings.
Sample and Test projects needed to add
```
implementation 'com.android.support:support-v4:27.1.1'
```
to ensure all dependencies use the same version.
Consumers of KMEA need to include Firebase and Crashlytics dependencies, but don't need to run the Google services. This simplifies these projects of not neeeding google-services.json.
Also added `-no-daemon` and `-debug` options to Samples and Test `build.sh` scripts so they can be run on CI servers.
Per Android Studio 3.0 [Release Notes](https://android-developers.googleblog.com/2017/10/android-studio-30.html)
-Update gradle version
-Change deprecated `compile` dependencies to `implementation` or `api`
-Change maven repositories to google (triplet plugin still on maven)
- Update readme instructions for using the engine
