Removed some deprecations

* Removed `The TaskContainer.add() method has been deprecated and is scheduled to be removed in Gradle 2.0. …` by updating the `gradle-nexus-plugin` to `0.3`.
* Removed `Creating properties on demand (a.k.a. dynamic properties) has been deprecated and is scheduled to be removed in Gradle 2.0. …` by removing the creation of this dynamic property.