Make test-projects runnable without test-kit

[mr-archano]

Problem

When a test-project fails is not possible at the moment just running that single project again, because of the way GradleRunner is using the java-gradle-plugin to inject the plugin into the classpath of the build.

Solution

Simply get rid of java-gradle-plugin and use composite builds instead. In order to achieve that I have introduced a Gradle project including the main sourceset of plugin. This project is then used by the test projects using a simple dependencySubsitution rule in their settings.gradle.

[tasomaniac]

Interesting approach. I wonder if the test plugin build is going to be cached between test runs.

[mr-archano]

Yes it does, I already checked :)