Catch errors while loading the conf.json

This PR fixes incompatibility bugs caused by MCPC+. Due to Forge modifying (adding mod blocks) to
Bukkit it will make the Materials enum unserializable by GSON.

Catching this error is not really a fix for that but it will prevent the factions plugin from crashing and not loading
while still being able to use the default config.

Gist error: https://gist.github.com/Maximvdw/c9cd852f2517bb539334