Add/remove components to entities in editor

[speigg]

We need to be able to add/remove components to entities in the editor.

• [x] remove components
• [ ] add components
• [ ] remove & add use commands & are undo-able
• [ ] change component order with grabbable draggable
• [ ] ensure all component combinations are safe
• [x] hide comopnent add/remove behind 'Advanced' mode