Block slopes and solid top things

[egordorichev]

Many blocks in the future, should work as platforms. This is called solid top blocks.
Also, thing to add is block slopes. We hae to variants of doing them:

• Only terraria-included ones.
• Top option + top corners, left slope, right slope and top-half slope.

Second one is not so good, because you will have to many variants, to hammer through.

[Col-E]

Adding a placeholder for something we don't know how is going to be implemented isn't going to be possible. It'll have to wait until a basic implementation is drafted up.