test(qb): Add missing tests for qb directory
* Add a GROUP BY test without Columns
* Add LtFunc test
* Add LtOrEqFunc test
* Add GtFunc test
* Add GtOrEqFunc test
* Add a Select with a AS between one column test
* Add a Order By DESC test
* Add Sum test
* Add Avg test
* Add Max test
* Add 2 tests for FuncColumn
* Add SetNamed test
* Add AddFunc test
* Add RemoveFunc test
* Add TTL and TimestampNamed test
* Add TTLNamed and Timestamp test
* Add TTL with negative or no duration test
* Add LtFunc test
* Add LtOrEqFunc test
* Add GtFunc test
* Add GtOrEqFunc test
* Add a Select with a AS between one column test
* Add a Order By DESC test
* Add Sum test
* Add Avg test
* Add Max test
* Add SetNamed test
* Add AddFunc test
* Add RemoveFunc test
* Add TTL and TimestampNamed test
* Add TTLNamed and Timestamp test
* Add TTL with negative or no duration test
* Add LtFunc test
* Add LtOrEqFunc test
* Add GtFunc test
* Add GtOrEqFunc test
* Add a Select with a AS between one column test
* Add a Order By DESC test
* Add Sum test
* Add Avg test
* Add Max test
* Add 2 tests for FuncColumn
* Add SetNamed test
* Add AddFunc test
* Add RemoveFunc test
* In qb/select.go, if there are no colums and the query have a GroupBy
statement then the query will be malformated.
* In qb/utils.go, refactor writeCql with a strings.Join call.
Fixes#78
