Implementing 'count' query type in \data\Model, misc. refactoring…

…s in MongoDB adapter, added support for count and group queries. Refactored `\data\model\Query` to support dynamic settings. Refactored `Query` setters to also return values. Added support methods for grouping and aggregation.

libraries/lithium/data/Source.php

@@ -159,6 +159,17 @@ abstract public function update($query, array $options = array());
 	 */
 	abstract public function delete($query, array $options = array());
 
+	/**
+	 * Returns the list of methods which format values imported from `Query` objects. Should be
+	 * overridden in subclasses.
+	 *
+	 * @see lithium\data\model\Query
+	 * @return array
+	 */
+	public function methods() {
+		return get_class_methods($this);
+	}
+
 	/**
 	 * A method which can be optionally implemented to configure a model class.
 	 *