Create 2d platformer with multiple levels to test simple game development pipeline.

[KonstantinTomashevich]

We need to create a simple 2d platformer in order to ensure that:

• We can work with multiple levels without problems.
• We can easily implement loading.
• Simplistic UI features is enough for platformer main menu and other menus.
• Current Celerity features and extensions are suitable enough for game logic.

Also, it is needed to draft architecture for planned game creation framework.

[KonstantinTomashevich]

As linked PR wasn't fully closing the issue, reopening it again.