Model test fixtures as a propert artifact
Previously they were modeled as just a file collection,
which confused the IDEA importer. They now use the more
canonical way of defining an additional artifact.
In a next step they should be reimplemented using variant
aware dependency resolution, so that we don't need a special
DSL to declare these dependencies.
13 Sep 18 6add47450a8453ace39a16a520c9a3b4c8789dce
Fix Gradleception build
Gradle 5.0 changes the behavior of BOM import, which is now required to be
imported explicitly using the `platform` keyword. However, this is not yet
available on the Gradle version we use to build, so this commit introduces
a temporary fix so that we can use the same syntax on all tested versions
07 Sep 18 6281c173abfad77cfe573b470389dae3156814ed