Nether type portals to any world determined by frame block type

[Nutmegan]

What would you like added? Similar to issue #26. Wondering if it would be possible for players to build portals that go to different worlds and the world they link to be determined by the a block type defined by the config. For example a player portal built from obsidian goes to the nether but maybe one built from purpur goes to the end, and one built from clay blocks goes to a mining world. All would use the same properties that current nether portals have available, but the frame type would define the world it is for.

Is it to solve a particular problem? Not really, I just think it would be a fun addition that makes travel between worlds more consistent.