Port optimizer selectivity changes to ColumnStore

Monty is working on optimizer changes which calculates timing estimates with a high precision using the cost of things such as index and disk access. It is likely to be merged soon in either 10.11 or 10.12.

This requires at the very least a minor patch to ColumnStore's handler class to compile and ideally some real cost based figures. The attached patch is against ColumnStore when using the bb-10.11-selectivity to get things to compile. There are 10 failures in ColumnStore's basic mtr when I tried this and some of them were a little odd to me, so this is where I'm handing it over.

If you want do full costings there is a tool called check_costs.pl in the tree which will calculate it for you on a table of 1M rows, see optimizer_costs.txt in the tree for more information. I've linked this ticket to the MDEV where the main work is happening.