[FEATURE] Import Scripted Classes

[lemz1]

DESCRIPTION

This pr adds the ability to import scripted classes like you would do in regular haxe, meaning:

package my.mod.game;

import game.ScriptedGame;
import my.mod.objects.ModdedPlayer;

class ModdedGame extends ScriptedGame {
  public function new() {
    var player = new ModdedPlayer();
  }
}

EXPLANATION

We create another imports variable to the PolymodClassDeclEx, because a script might import a class that hasn't been registered yet.
After all classes have been registered and parsed, we validate the imports. If the import still can't be found we give the user an error.

[AbnormalPoof]

Yes please

[cyn0x8]

will #201 replace this? or is it a separate thing
i see "ability to extend scripted classes" but idk if this implies the ability to import or not

[lemz1]

will #201 replace this? or is it a separate thing i see "ability to extend scripted classes" but idk if this implies the ability to import or not

#201 does implement importing scripted classes. So i guess #201 would also replace this pr.