Update textures to be more understandable

Advanced Solar Generator:  Removed the gray parts at the bottom, leaving
only one red "output port".
Wind Turbine:  Added an "output port", since it did not have one.

I also changed the red block to a green one (now it looks similar to the
green energy inside the universal cables)
Merge pull request #877 from Mierzen/development

Update textures to be more understandable