Syntax ECS

[kvark]

Closes #3

This is a struct decorator to be used like this:

#[plugin(secs)]
extern crate id;

#[secs(id)]
struct Prototype<T1, T2> {
    name1: Component1<T1>,
    name2: Component2,
}

It generates the same Entity, Components, World as before but with several bonuses:

• proper generics support (#3)
• visibility inheritance (for the whole ECS and potentially even single components)