Added example of a biopet executable

external-example/src/main/scala/org/example/group/ExecutableExample.scala

+package org.example.group
+
+import nl.lumc.sasc.biopet.core.{ MainCommand, BiopetExecutable }
+
+/**
+ * Created by pjvanthof on 30/08/15.
+ */
+object ExecutableExample extends BiopetExecutable {
+
+  /** This list defines the pipeline that are usable from the executable */
+  def pipelines: List[MainCommand] = List(
+    org.example.group.pipelines.BiopetPipeline,
+    org.example.group.pipelines.SimplePipeline
+  )
+
+  /** This list defines the (biopet)tools that are usable from the executable */
+  def tools: List[MainCommand] = Nil
+}