Add compileOrder into the org.scala-ide.sdt.core.prefs file

Fix to honor the compileOrder := CompileOrder.JavaThenScala directive in the build.sbt, Re Issue: #218

I'm not super happy with the code, but it gets the job done.  Scalaz doesn't have a typeclass for Seq, so had to convert to a Vector in order to use the built in append operator in Validation