Makes temporary permissions work

Saves and loads temporary permissions to/from disk as necessary
Gives players their temporary permissions when joining
Adds an un-used config file
Changes an english string in strings.yml

src/main/resources/config.yml

@@ -0,0 +1,5 @@
+# The language to use for the plugin
+language: en
+
+# Whether to only give permissions for a single world, instead of granting permissions for all worlds
+perWorldPermissions: false