update `Spacegray` to support sidebar icons

Icons from default / Soda / a download from a user of the sublime text
forum.
Darken the file icons
Update icons
Add a ton of more icons

credits go to https://github.com/pryley/soda-theme and
https://github.com/facelessuser/Aprosopo/tree/master/icons
better tint on the icons
Correct tiny mistakes
removed icons