[SPARK-1681] Include datanucleus jars in Spark Hive distribution

This copies the datanucleus jars over from `lib_managed` into `dist/lib`, if any. The `CLASSPATH` must also be updated to reflect this change.

Author: Andrew Or <andrewor14@gmail.com>

Closes #610 from andrewor14/hive-distribution and squashes the following commits:

a4bc96f [Andrew Or] Rename search path in jar error check
fa205e1 [Andrew Or] Merge branch 'master' of github.com:apache/spark into hive-distribution
7855f58 [Andrew Or] Have jar command respect JAVA_HOME + check for jar errors both cases
c16bbfd [Andrew Or] Merge branch 'master' of github.com:apache/spark into hive-distribution
32f6826 [Andrew Or] Leave the double colons
940a1bb [Andrew Or] Add back 2>/dev/null
58357cc [Andrew Or] Include datanucleus jars in Spark distribution built with Hive support
(cherry picked from commit cf0a8f0204bb8acdaf441b03c924c278fef08e28)

Signed-off-by: Patrick Wendell <pwendell@gmail.com>