Simple entity editor in nfEngineDemo

[Witek902]

nfEngineDemo should have a simple integrated Editor. Features:

• [ ] Picking an entity will select it and enable an Editor window, which will list all components attached to it.
• [ ] Editing the properties and adding new components will be possible.
• [ ] DebugRenderer will draw icons for non-meshed entities (ex. LightComponent) to ease the picking process.

More features are subject to discuss.

The task should be done after Picking is implemented.