belongs_many_many improvements

+ added support for dot-notation in belongs_many_many
  Example:
  static $belongs_many_many = array(
  	'BelongsManyMantRelation' => 'Class.ManyManyRelation'
  );
  You can use notation without '.' as well. Needs patched sapphire 2.4
  framework (https://github.com/lazyeugene/sapphire/tree/2.4).
  Works in the old way without one's patches.