Changelog: Health and entity system

This is a big update, that comes with many improvements to the game engine, but not many new features. This is necessary to allow future improvements, like the introduction of mobs.

Meanwhile I'm also working on the story, which is not yet part of the game.

Gameplay changes

• Added a health system

• Implemented death and respawn

• Added a robot printer in the factory bay

• The player drops robot parts when dying

• The player looses health if it falls from too high

• The gravity beam cannot counterbalance an infinite amount of velocity anymore

• The player explodes when it dies, pushing away nearby drops and entities

UI changes

• Added a health bar

• Added customized window borders

• Changed the color and font of the texts

• Adjusted spacing in the toolbar

• Added missing tech tree items and sorted the existing elements

• Fixed wrong output icon in some recipes (for the saw and the mold)

• Moved the developer command prompt to the right

Engine changes

• Unified the drops and player code into a single physics engine

• Moved part of the game definitions to json files, which allows for limited modding

• Lots of code refactorings and architectural changes, improved the overall maintainability of the code

Bugfixes

• Fixed crash when trying to use fruits

• Fixed a memory leak occuring when failing to load a save file

• Fixed crash when creating an empty world in the editor

• Fixed camera bug when moving to another world

Trivia

• Added a tilting animation when moving

• Re-adjusted the player and gravity beam's hitbox and position

• Added an animation on the robot arms when changing the selected tool

• Added a wind sound effect when falling from the orbit

(version d3816ad3)