#482 Provide better default messages and merge MessagesManager

- Return message from the JAR's messages_en.yml file instead of an unusable error for the end user
- Merge MessagesManager into Messages

src/test/resources/messages_default.yml

@@ -0,0 +1,5 @@
+# Simulates a default file
+
+wrong_pwd: 'This message is overridden in messages_test.yml'
+reg_only: 'Message from default file'
+logged_in: '&cYou''re already logged in!'

src/test/resources/messages_test.yml

@@ -1,3 +1,5 @@
+# Sample messages file
+
 unknown_user: 'This test message&nincludes&nsome new lines'
 unsafe_spawn: '&cHere we have&bdefined some colors &dand some other &lthings'
 not_logged_in: 'Apostrophes '' should be loaded correctly, don''t you think?'