- clean up
- the structnode ids must be int

DispatcherOnChange and DispatcherOnSet now hold weakreferences of the actions
Ticker is now deprecated, a legacy copy will be found in the example
Added Engines Profiler Tool
Added the concept of Entity Group (more will follow on the subject in an article)
Handling the creation of entities inside the Add Methods
fixed some bugs
renamed namespace to Svelto.ECS
add the concept of ExtraImplementors for the EntityDescriptor

Updated Context and Ticker Framework
Added Datastructures