IMPALA-887: Improve partition pruning time (final)

This commit contains the final set of changes for improving the
performance of partition pruning. For each HdfsTable, we materialize a
set of partition value metadata that allows the efficient evaluation of
simple predicates on partition attributes without invoking the BE. These
changes result in three orders of magnitude performance improvement
during partition pruning.

Change-Id: I5b405f0f45a470f2ba7b2191e0d46632c354d5ae
Reviewed-on: http://gerrit.ent.cloudera.com:8080/2700
Reviewed-by: Dimitris Tsirogiannis <dtsirogiannis@cloudera.com>
Tested-by: jenkins