This commit make the Xray option for the wireframe different from the other
shading mode. This makes it possible to rapidly switch between wireframe +
Xray and Solid mode without Xray.
Xray alpha is also decoupled.
Both variables are duplicated and exposed separately through RNA.
OpenGL rendering only implemented the deferred renderer. This commit
will add the forward renderer. The forward renderer is used when XRay
mode is enabled
This is intended for quick renders for previsualization, animation previews
or sequencer previews. It provides the same settings as found in the 3D view
Shading popover in solid display mode, but in the scene render properties.
The "Workbench" engine was removed, and this name no longer appears in the
user interface, it's purely an internal name. We might come up with a better
name for this OpenGL engine still, but it's good to be consistent with the
OpenGL Render operator name since this has a similar purpose.
