[feature request] Make it possible to use a texture to 3d view

[milasudril]

Summary

Add a selector to use RGBA data as a texture.

Motivation

When generating landscapes, the terrain data can be used to generate a suitable texture. Make it possible to preview a generated texture when previewing terrain.

Proposed solution

A vertical panel to the left the actual view would do. Note: This panel may also host other widgets for camera control.

Roadmap

• Make sure it is possible to render from more than one node
• Add a 3d view control panel
• Add texture sampler to shader
• Add functionality to upload texture from CPU to GPU