Fixed models for some tuff-brick blocks

[shaijana]

The models for "tuff_brick_stairs", "tuff_brick_slab" and "tuff_brick_wall" were missing, so this blocks were not shown on the map. In addision the models for "polished_tuff_stairs" and "polished_tuff_wall" were duplicated, so maybe an copy&paste-mistake.

[hmlendea]

I'm curious why this wasn't merged yet? People have been using the new blocks a lot for a while now, and some builds look very strange. On my server there's one city in particular that uses a lot of tuff, and it looks very broken on the webmap.

[awbuckst11181999]

I am having the same issue, please look into fixing this!

[Strahilchu]

Also having this issue

[mikeprimm]

Looks good - thanks!