Updated gradle to 2.2 and also upgraded all dependencies. Needed to add checker framework in order to have JSR-308 annotations available.
Implemented a integration-test Gradle plugin.

This deprecates the 'prototype-integration-test' module. All integration test code has moved to the 'prototype-app' directly. Hopefully this will cause the coverage data taken into account by 'jacoco' plugin. The 'integration-test' plugin will be extracted and published in the next step.
Now using the EWERK integration-test plugin from Gradle plugin portal.