created Builder directory to keep builders for each db type.
moved Bind and Quote class under Builder directory.
they are mainly used during sql build process.
renamed Query to Sql, since this is THE SQL class.
moved Sql and Where under Sql namespace.
renamed namespaces after move.
Query contains Sql and Builder.
add Factory class; use the factory in tests.
limit the visibility of builders for not-so-used objects.
swapped $quote and $bind argument; bind is far more important than quote.
removed (that ugly) setDbType method.
or does not set parenthesis flag to true.
removed unused required packages; SqlBuilder does not access to db, anymore.
maybe rename from id_name to keyName.
and setting table alias when setting table name.
write some usage, and some wishes came true.
setting builder as optional.