Add Oracle, SQL Server, MySQL Compatibility functions.

https://forums.couchbase.com/t/simulate-sql-coalesce-and-isnull-using-n1ql/16725

This is to make people and product migration easier.

Consider requirement of these functions on JSON types, include arrays and objects where applicable.

Add Coalesce, NVL, NVL2, etc functions to N1QL.

Analyze Oracle and SQL Server for missing (common!) functions in N1QL and propose the list to review.

-- 

   | COSH--- |   
   | SIN---- |   
   | SINH--- |   
   | TAN---- |   
   | TANH--- |   
   | 'DEGREES' |   
   'ASIN+(-
numeric_expr
-)+-'   
    | ASINH |    
    | ACOS- |    
    | ACOSH |    
    | ATAN- |    
    | 'ATANH' |    
    +ATAN2(-
y, x
-)------------+    
    'RADIANS(-
degree_expr
-)---'