Add a configuration to print jdbc exceptions

By default, mcmmo tries to pretty print errors, which is fine for many cases,
however; deeper nested errors can lack information, e.g. networking related issues,
while the pretty print is less intimitating and provides useful information to users,
surpressing the trace can prevent debugging these deeper issues, this config option serves
as a compromise between scaring users and having a means to find these deeper issues.

src/main/resources/config.yml

@@ -146,6 +146,7 @@ Backups:
 ###
 MySQL:
     Enabled: false
+    Debug: false
     Database:
         User_Name: UserName
         User_Password: UserPassword