#58 Fixed clean.dependsOn grails-clean

Issue58
https://github.com/grails/grails-gradle-plugin/issues/58

Gradle forums threads:

http://forums.gradle.org/gradle/topics/cannot_set_tasks_dependencies_on_task_clean_base_plugin?utm_content=reply_link&utm_medium=email&utm_source=reply_notification#reply_13739452