Oh well, even if you didn't put your log on pastebin correctly...
java.lang.IllegalArgumentException: Could not get provider type for dimension 8, does not exist
That means you made some sort of Mystcraft dimension or some other thing, and then it got corrupted.
Just go to your /serverFolder/saves/MyWorldName/ and delete the folder called DIM-8.
Remember though, if it's an important dimension it's not my fault. It's world corruption's fault. Backup the DIM-8 folder, just in case you need it.