Logs: Give an ID to each events chain

[jacomyal]

Sometimes, several different events chains can be executed in parallele (when using before in services, for instance). Then, the log can look like:

...
[myDomino] Iteration 1 (main loop)
[myDomino]  -> Events:  ["anEvent"]
[myDomino] Iteration 5 (main loop)
[myDomino]  -> Events:  ["anotherEvent"]
[myDomino] Iteration 6 (main loop)
[myDomino]  -> Events:  ["yetAnotherEvent"]
...

It might be useful to have each chain having an ID displayed, like this:

...
[myDomino] Iteration 1 (chain 2)
[myDomino]  -> Events:  ["anEvent"]
[myDomino] Iteration 5 (chain 1)
[myDomino]  -> Events:  ["anotherEvent"]
[myDomino] Iteration 6 (chain 1)
[myDomino]  -> Events:  ["yetAnotherEvent"]
...