#129 reverse system dispose and entity onRemove order.

[metaphore]

Follow up for #129

• Call system dispose in reverse order
• Call FamilyOnRemove.onRemove(entity: Entity) in reverse order (depends on the bound system).
• Dedicated tests for system execution order.

I'm not sure what's the best way to do a reverse "for" loop on an array in Kotlin. Sounds like there's no built-in singular function for that, and I didn't want to use something that may create an iterator or do unnecessary allocation like collection.asReversed().forEach(). So I added an inline extension function forEachReversed() at the end of the world.kt file. Don't know if there's any better place.

@Quillraven please let me know if there's something wrong with it and if it needs to be changed/moved.

[Quillraven]

You are correct that there is no build in function. The only one that I found is:

for (i in array.indices.reversed()) {
    println(array[i])
}

According to bytecode it looks like this is a simple for loop without iterator or other objects.

I personally would just use that without a separate extension function but your way is also fine.

[metaphore]

I forgot, but it would be good also to update the FamilyOnAdd.onAdd() and IntervalSystem.onDispose() docs to reflect the reverse order of those functions.