* Added all postgres window functions and tests
* Refactored the naming of aggregate functions
* Added field to calculate number of stddevs
* Refactored tables into subclasses

* Delegated some processing to field class
* Added template methods into table class
* Refactored table method names
* Added simple inner query testing
* Properly handle deeply nested inner query names and arg naming
* Properly update outer query args
* Updated test to reflect table naming change