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/initialization/OnShutdownPlayerSaver.java

@@ -76,10 +76,8 @@ public class OnShutdownPlayerSaver {
             dataSource.updateQuitLoc(auth);
         }
         if (settings.getProperty(RestrictionSettings.TELEPORT_UNAUTHED_TO_SPAWN)
-            && !settings.getProperty(RestrictionSettings.NO_TELEPORT)) {
-            if (!limboPlayerStorage.hasData(player)) {
-                limboPlayerStorage.saveData(player);
-            }
+            && !settings.getProperty(RestrictionSettings.NO_TELEPORT) && !limboPlayerStorage.hasData(player)) {
+            limboPlayerStorage.saveData(player);
         }
     }
 }