Adds three extra methods to Data/SQLQuery query that allow for starting
a disjunctive subgroup, a conjunctive subgroup and for ending a subgroup.
Database::sqlWhereToString() now builds up the WHERE clause one by one
instead of with a straight implode. Uses a stack to know which conenctive
to use.
If the applyRelation() was passed a relation that went to a class with a parent
class with a database table, applyRelation would return the name of the parent
class, rather than the class the relation was actually too.
