Use some macro reification
more macro reification -> simplier node macros
Generate dispatch function for signals via macro
Avoid creating GenericListIterator objects for signal dispatching. This should speedup things alot.
Add inlines for Entity/Node/SystemList iterators and provide iterator type.

This way new haxe (3.1+) can optimize iterator into local vars instead
of creating iterator object which will speed up things greatly.
Add TODO on performance.