Missing method update on the compound metric class

signed-off-by: Thiago Kenji Okada <thiago.mast3r@gmail.com>
Added unit tests for the update method

signed-off-by: Pedro Paulo Vezza Campos <pedro@vezza.com.br>
Added acceptance test to Compound Metric edit configuration

signed-off-by: Pedro Paulo Vezza Campos <pedro@vezza.com.br>