Fix various code issues as detected by Sonar

Mostly minor changes:
- Add deprecated javadoc tag on deprecated members
- Reduce duplication (FlatFile, BackupService, ...)
- Make methods static
- Reduce size of anonymous classes
- Replace name with displayName in PermissionsSystemType (avoids confusing with Enum name())
- Tabs to spaces
- Merge if statements

Code from third-party sources (BCryptService, BinTools, PHPBB) not modified.

src/main/java/fr/xephi/authme/process/changepassword/AsyncChangePassword.java

@@ -27,7 +27,8 @@ public class AsyncChangePassword implements AsynchronousProcess {
     @Inject
     private PlayerCache playerCache;
 
-    AsyncChangePassword() { }
+    AsyncChangePassword() {
+    }
 
 
     public void changePassword(final Player player, String oldPassword, String newPassword) {