Removed parameter count check since ADD_MONTHS has only two parameter

revamp the selection of indexes to move the bulk of the costing into
BaseIndex.
In the process, clean it up and modify the costing so that when using a
covering index, we pick the index with the least number of columns.
Smaller indexes are faster to load, leading to lower retrieval costs.

Fixed misspelling
Renamed ToDateParams to ToDateParser
Code cleanup

when we can satisfy a query from an index without touching table data,
then that index should have a lower cost than an index that DOES need
to retrieve table data

OptimizerHints dropped in favor of SET FORCE_JOIN_ORDER setting, fixed join order in case of TableFilter reorderings by Parser, added more tests.

method