Make column references in SQL strings and column lists case insensitive

[wjones127]

When coming from languages that use camel case, such as TypeScript, it's easy to create datasets with mixed-case column names. However, it seems that our SQL parser works only with lower case, and to match any mixed case requires wrapper in backticks.

This also is an issue with column lists, such as the on parameter in merge insert. It's current impossible to use a mixed-case column as the join key in merge insert queries.