Editor hides texture layers when new map shader is present

[BlackYps]

When the map shader is anything else than TTerrainXP it hides the upper four layers. This was okay in a time where there was only the extended and the basic shader. But now we have more terrain shaders and the default should be to show all texture layers.
Or to properly detect the used shader for that matter.

[BlackYps]

Fixed in #42