v0.5.0 - Renewal

After all this work, I wish I had something more exciting to talk about, but this release is mostly a lot of internal rewriting to support one relatively small but important feature: Sprite sheets. This feature is the base of a bunch of higher-level features, like tile maps and sprite animations, which I hope will be my next big features to develop (as I build an example Sokoban game).

Other changes in this release include:

• Asset system, so individual files can provide multiple game assets
• Bugfixes that prevented the Prefab editor from working right
• Fixes to the Scene Entity tree so that entities can be rearranged and reordered
• Fixes to the Space Shooter example (still a work-in-progress)