Color and sorting of categories and blockls

[meliurwen]

Looking at the Blockly toolbar a couple of changes to propose came to my mind:

• Each category has assigned its own well distinguishable color.
• Categories should be listed in descending order by relevance (implying we have a definition of "relevant" in this context) form top to bottom; same thing for blocks within the categories.

If I remember correctly it's a pretty safe and easy thing to change (edit the xml files in the src/assets/ folder).

[avivace]

Makes a lot of sense and I think it'll be a nice quality of life improvement.

However - we are holding this up until #45 is implemented and there's a reproducible and usable way of editing toolboxes.

[previ]

related to #45 can be considered implemented in the toolbox editor