Issues #288, #289, #290, #311

Issues in this pull request
1.	STDDEV_POP support
2.	STDDEV_SAMP support
3.	PERCENT_RANK support for finding rank on a hypothetical value (Not for every column)
4.	James comments rework 
5.	Support to specify the max and min values(like default) on  BuiltInFunction #Argument ..