Add EventManager

[Thinkscape]

The library is lacking a proper EventManager. I'd like to be able to short-circuit all operations, inject values and lambdas with transformations before the value is processed.

Of course it must be based on a priority stack and possibly allow proxying. We could also use some experimental lambda serializer for storing lambdas in Elastic Search.

[slaFFik]

+1

[monobook]

+1