Swimlanes support to Activiti Modeler

Notes:
 - Added the missing javascript code to handle Pools and Lanes. I did not understand why this code are not on Activiti Modeler, since it is Signavio Core Components based;
 - Based on Activiti Designer, I replace the pool stencilset properties with the process properties, such as `process_identifier` and `process_executable`;
 - `SequenceFlow` are not referenced by Lanes, so they need to included separately;
 - The `outgoing` property is required by Oryx.