ExceptionCatcher should be put before MaxMessages et MaxExecutionTime pr...

@blaugueux I made this modification according to your changes in swarrot/swarrot#37.

Both MaxMessagesProcessor and MaxExecutionTimeProcessor need to be added in the stack after the ExceptionCatcher, otherwise the raised exception prevent them to make their job.

For example, if you want to consume only 1 message, if this one throw an exception, the process continue as the `messagesProcessed` property isn't updated.
I know it's just to be consistent with the rest of the class. :)