Support quoted quotion marks within identifiers

[crisptrutski]

In SQL you can include the quote character within an identifier name by repeating it, e.g.

`schemer`.`the-table`.`doug``s mug`

{:schema "schemer"
 :table  "the-table"
 :column "doug`s mug"}

Metabase solves this with a slightly more complex quote stripper which we should be able to simply pilfer.