DRILL-398: Fix build/packaging issues with storage-hive jars
1. Remove hive-exec dependencies from root pom.xml and move hive-hbase dependency to contrib/storage-hive/pom.xml. Idea is to download all required hive dependencies through storage-hive artifact.
2. In distribution/pom.xml exclude hive-exec jar from storage-hive dependency. Storage-hive jar already contains the shaded hive-exec.
3. In contrib/storage-hive/pom.xml add a target to unpack the classes in storage-hive.jar into contrib/storage-hive/target/classes directory. Unpacking is needed because when you run 'mvn test' from root directory, dependencies within the project (such as protocol or storage-hive) are resolved to target/classes directory instead of jar. This is by design in Maven. If we don't unpack, we get class not found errors for classes in storage-hive.jar while running tests only.
