CBO: provide a mechanism to test CBO features based on table stats only (w/o table data)

Since lot of the CBO work is focused on planning, it will be nice to be able to run explain query to test CBO features. TPCDS has a rich enough schema and query set. So the patch loads a dump TPCDS(Scale 10000) stats.

1. TestCBO shows a way to load stats from a dump and run explain on a tpcds query. The output is currently dumped to Sys.out. This can be improved by hooking to QTestUtil, but hopefully this is a good start.

2. Uncovered couple of issues in the process of testing this:
a) PartitionPruner fails on 'true' constants. For e.g. you will get an error for

SELECT * 
FROM t WHERE
partCol < 100 AND true

This gets exposed because the predicates coming out of Optiq can contain 'true' predicates.
b) OpTraitsRulesProcFactory:checkBucketedTable checks that number of files = numBuckets. This fails because there are no dataFiles. So I have altered it to catch exceptions and assume bucketMapJoinConvertible = false if an exception is encountered here.
Uploading with these changes in this patch for now. Will carve them out as separate patches.

Ashutosh Chauhan, Gunther Hagleitner can you please take a look.