Added support for Query Defined Tables (Sub-Queries)

[enragedbunny]

In order to support my own uses for this, I needed to be able to correctly examine SQL files that had sub-queries as FROM statements. In order to support this, I added a function to recursively go through the object to find the first table reference within any number of nested sub-queries. I also provided an example file. I have only tested this on SQL code examples I have available, so I am not sure if this introduces issues with other valid SQL or not.