Add support for multicolor textures with fixed display of textures

Now the textures might be multicolor. The textutre have to be placed in data/name.txt and the color of each "pixel" in data/name.col. The color is just the first letter of the color name, e.g. data/ladder.txt:
```
|=|
|=|
|=|
```
data/ladder.col
```
mym
mym
mym
```
will give you a magenta ladder with yellow rungs.