GUI Complete rework

[fabianmakila]

Since we're missing any source files for the original gui textures it's currently very time consuming to create new GUI textures. Our current textures have some copy past artifacts and they are not really consistent.

The old textures were likely created by overlaying a texture on top of vanilla gui and some manual decoration.

The way we plan to approach this is we'll first create a base texture which we can then build upon the required GUI elements.