DRILL-5065: Optimize count(*) queries on MapR-DB JSON Tables
In MapR-DB v5.2.0, we enabled '_id' only projection for JSON
tables. Hence, we can now optimize the following queries:
a. count(*) by projecting only the '_id' column.
b. '_id' only projections, including count(_id)
Change the format plugin config parameter name.
Fix setter of config parameter `disableCountOptimization` for drill-maprdb plugin
closes #678
