IMPALA-951: Throw parser error if no partition spec specified in ALTER TABLE ADD/DROP PARTITION

Change-Id: I876423e39d858d602ed0fbe8369a6714c82639d8
Reviewed-on: http://gerrit.ent.cloudera.com:8080/2295
Reviewed-by: Alex Behm <alex.behm@cloudera.com>
Tested-by: jenkins