rewrite the common and colors shaders in a better way

[illwieckz]

This doesn't fix any bug neither bring new features, it just does things in a better way.

• urcheon: properly copy the transparent tga
  The transparent image is used in editor. An 1×1 TGA is the smallest image format.
• materials: use map instead of diffuseMap, there is no lightmap to use
• materials: use engine builtin images
• materials: rewrite portal and mirror using a builtin image

It requires:

• Do not assume shaders without a stage is fog DaemonEngine/Daemon#1806

Even though it is not required to merge that engine PR on for-0.56.0/sync, we should not distribute this change in a point release as older engines would not render those materials properly.

[slipher]

Why are you adding a stage?

[illwieckz]

Likely a rebase mess.

[slipher]

If you ask me _red should be nuked. Just use rgbgen const (1 0 0)

[illwieckz]

Done.

[illwieckz]

Now all the colors shaders use either:

• $white (white)
• $black (black)
• $white + rgbgen const (all remaining colors)
• no stage (fully transparent)

None of the colors images are now expected to be loaded by the Dæmon engine. They are shipped to be used as qer_editorImage which is meant to be used by both the NetRadiant editor end the Q3map2 map compiler (qer_editorImage being the only syntax meant to be understood by them).