Add new analytic functions: CUME_DIST, PERCENT_RANK, PERCENTILE_CONT

Please, add the following functions:

CUME_DIST, PERCENT_RANK, PERCENTILE_CONT

https://msdn.microsoft.com/en-us/library/hh231078.aspx
https://msdn.microsoft.com/en-us/library/hh213573.aspx
https://msdn.microsoft.com/en-us/library/hh231473.aspx