Billboard Component

[judysng]

Adds the billboard component (+ template files) which takes material & mesh paths in BillboardComponentController.cpp.

Draft for now because I got the component working, but I ran out of time to make more improvements on the code & tutorial, like:

• Using MaterialReceiver Bus instead of using hard path code
• Adding fields to the component and adjust the code based on that
• Using TickBus instead of SceneNotificationBus?
• Adding more visible steps to the tutorial (like people can check their work)