Gradle support for IntelliJ 2016

[ncoelle]

As discussed at the Gradle Support Forum the gradle plugin 'idea' is not working optimal when performing ./gradlew idea and opening the project with IntelliJ 2016.

I removed the plugin from build.gradle. Just opening the bdd-security project with IntelliJ 2016 works fine. I did not perform a pull request because I am not sure which implications this might have on the bdd-security roadmap.