Don't overwrite invalid spigot.yml
Fix misnamed function causing oddities in mountables
Ease ClassLoader Deadlocks Where Possible

When on Java 7 we can register the classloader as parallel capable to prevent deadlocks caused by certain scenarios. Due to the nature of PluginClassLoader this isn't completely safe, but we can make it safer by switching to concurrency focused collections. Either way this is far better than crashing the server.
Rework the block place limit to be based on the packet's arrival time instead of the server's current tick.

This should help with low tps servers/high latency connections
Cache skull skin blobs instead of looking them up each time
Make "moved wrongly" limit configurable