Improve loading of files (use Path, move standard assets)

[maeda6uiui]

Overview

Following changes have been made:

• Methods to create a component now takes a Path object
• Standard assets have been moved to Mechtatel directory (outside the JAR)

Methods to create a component that previously took a URL object now takes a Path object instead.

defaultScreen.createModel(Paths.get("./Mechtatel/Standard/Model/Cube/cube.obj"));

For the sake of this change, standard assets other than shaders have been moved to Mechtatel directory, and they are not going to be packaged in the JAR in future releases.