For Travis CI - test run Android APK in emulator as part of CI build.
This should prevent the similar incident like SONAME breaking Android APK went unnotice for days.
Also:
- Revert back the workaround attempt for the RPI build as it did not work. The build error problem has been reported to Travis-CI upstream issue log.
- Add new rake task to automate Android APK testing (tested on Linux platform only).