Android Archive library release

• Core engine now builds as a standalone .AAR file to allow for easier integration in custom projects
• OpenSL and AAudio drivers can be switched at runtime with AAudio side loading when running on SDK level 26
• Unit tests are now integrated with Gradle builds to be available during development

Production ready multi driver release

In this version:

• Full OpenSL and AAudio driver support
• Production ready engine stability
• Gradle based toolchain with dependency on CLI based builds of the native library

Caveats:

• AAudio support only when compiled at sdk level 26 (addressed in bfc68c5)
• Audio drivers cannot be switched during application lifetime (addressed in 7ab3d10)
• Unit tests can not be executed during development (requires separate build and cleaning of caches, addressed in 7ab3d10)