SPARK-5557: Explicitly include servlet API in dependencies.

Because of the way we shade jetty, we lose its dependency orbit
in the assembly jar, which includes the javax servlet API's. This
adds back orbit explicitly, using the version that matches
our jetty version.

Author: pwendell

core/pom.xml

@@ -132,6 +132,13 @@
       <artifactId>jetty-servlet</artifactId>
       <scope>compile</scope>
     </dependency>
+    <!-- Because we mark jetty as provided and shade it, its dependency
+         orbit is ignored, so we explicitly list it here (see SPARK-5557).-->
+    <dependency>
+      <groupId>org.eclipse.jetty.orbit</groupId>
+      <artifactId>javax.servlet</artifactId>
+      <version>${orbit.version}</version>
+    </dependency>
 
     <dependency>
       <groupId>org.apache.commons</groupId>

pom.xml

@@ -135,6 +135,7 @@
     <parquet.version>1.6.0rc3</parquet.version>
     <jblas.version>1.2.3</jblas.version>
     <jetty.version>8.1.14.v20131031</jetty.version>
+    <orbit.version>3.0.0.v201112011016</orbit.version>
     <chill.version>0.5.0</chill.version>
     <kryo.version>2.24.0</kryo.version>
     <ivy.version>2.4.0</ivy.version>