Add Decanter made EventAdmin impl

[jbonofre]

Currently, Decanter is using EventAdmin spec. The default EventAdmin implementation we are using is the Felix one.

With the amount of data Decanter can deal with, Felix EventAdmin doesn't fit so well (memory usage, timeout, etc).

We should use Decanter implementation of EventAdmin fitting the Decanter requirement:

• deal with large amount of data
• optional persistency
• externalized messaging (AMQ, Kafka, ...)

[fpapon]

If we are talking about internal event in Decanter I'm not sure it's a good idea to deal with externalized messaging, even if it's optional because Decanter is a pure collector. If the user want to send data to externalized messaging, he can use the dedicated appender to do it.