Use ordinal order of columns for mysql

[Recodify]

This is a fix for the following, implemented for mysql only, similar fixes possible for pg and mssql but I don't have instances handy to test.

Please note, this fix will only work with a blank db as column orders are cached in the sqllite db. Simple fix: delete querytree.db in root.

https://github.com/d4software/QueryTree/issues/81