Blender Git Loki

When creating texture/image in Texture Paint mode, both datablocks should get the same name

The paint slot name was not the same as what is displayed on the texture properties panel.
Instead, the slot type (e.g. "Diffuse Color") was used as the name.

Patch by Suchaaver (@minifigmaster125) with minor changes from @mont29.

Reviewers: mont29, sergey

Maniphest Tasks: T50704

Differential Revision: https://developer.blender.org/D2523