activate(mPropertyBag) {
			return _getWriteConnectors()
			.then(_executeActionByName.bind(undefined, "versions.activate", mPropertyBag));
		}
Activates the draft for a given application and layer.

@param {object} mPropertyBag - Property bag
@param {sap.ui.fl.Layer} mPropertyBag.layer - Layer
@param {string} mPropertyBag.reference - Flex reference
@param {string} mPropertyBag.title - Title of the to be activated version
@returns {Promise<sap.ui.fl.Version>} Promise resolving with the activated version;
rejects if an error occurs or the layer does not support draft handling