Remove RemoveSortRule and PushSortPastProjectRule during Drill Logical planning phase.
fix NPE in merging receiver
Add support for non-equijoins in the presence of other equijoins between the same tables.
Specify target traits based on converted RelNode's trait, in stead of empty trait sets, when call planner to get the logical plan.

Add back RemoveSortRule to Logical rulesets.
Create custom parser for Drill using Optiq's parser grammer file
Adds parsing support for SHOW TABLES, SHOW DATABASES/SCHEMAS
   and DESCRIBE TABLE