Adds /paper command for reloading the paper config.
Closes GH-639
Per-world config logging has been removed in favor of all or nothing
logging for all paper settings. I don't believe it was used enough to
warrant maintaining. If this is not the case it should be possible to
re-add it.
I misread the code and thought the code kept looping until the mob spawn cap was hit.
Upon furthur review, this is not true, so this patch doesn't do anything sane.
Use -1 to represent vanilla/unlimited.
Updated PaperWorldConfig to also update the individual worlds limit if it was set
to the new default value.
Should hopefully help #235
