Allow triggering of several graphs by one incoming envelope
Created originally on Bitbucket by cdevienne (Christophe de Vienne)
In some case a single envelope will be transformed in many different ways to reach many consumers. Being able to define a graph for each transformation/consumer would make it safer to maintain such a setup.
This change concerns graph, process and broker. Once each process is initiated, the rest should work without modification.
To make it safer, we can add an 'exclusive' attribute on source nodes, defaulted to 'true', that would prevent unwanted multi-match of graphs.