Add the keyword depends-on-plugin.
Implement the depends-on-plugin directive for Groovy, Clojure and Scala.

Analogous to "// add-to-classpath /some/path/my.jar", the newly added
"// depends-on-plugin other-plugin-id" can be used to simulate the
<depends/> element from plugin.xml.
Modify the ScalaPluginRunner to include all JAR files of all plugins in the classpath.

This is required to work around the fact that the Scala Interpreter
requires the .class files for classes that are used statically,
instead of being able to use the ClassLoader for this.