Feature/multi component

[freezy]

This PR splits the game item data into multiple components. It closes #181 and closes #165. For a more detailed description of what it does, check #165, user documentation can be found here.

Very briefly, what has been done:

• Authoring components are now split into main, collider, mesh, and animation components.
• Parenting a component to another will add the behavior to the parent, i.e. events will emitted through the parent, and movement applied relative to the parent (this worked before)
• Parenting isn't possible for all combinations - unsupported combinations will show an error in the inspector.
• When importing, items get automatically parented based on a naming convention.
• All components have icons. Orange for main, blue for mesh, and green for collider and animation.
• Mesh components are now solely responsible for generating the mesh. That means RenderObjectGroup isn't used anymore, and renderables are now able to produce partial meshes (instead of only the entire group like before)
• Wires of wire ramps are now merged into a single mesh
• All strings in data are string.Empty per default to avoid NPEs
• Images in documentation can now be zoomed in with a lightbox
• New icon for coil manager
• Collision debug manager is gone, collider debug is now available in the collider inspectors individually
• Every authoring component has now its own inspector

TODO

• Enable remaining parenting combinations
• Validate parenting combinations on import
• Proof-read documentation (thanks @ecurtz!)
• Developer documentation of class schema?
• Components aren't opened automatically anymore - fix?
• Fix Undo when manipulating collider or mesh components
• Handle layers correctly