Function BuildSelect

BuildSelect work as its name says. supported operators including: =,in,>,>=,<,<=,<>,!=. key without operator will be regarded as =. special key begin with _: _orderby,_groupby,_limit,_having. the value of _limit must be a slice whose type should be []uint and must contain two uints(ie: []uint{0, 100

(table string, where map[string]interface{}, selectField []string)