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/register/ProcessSyncEmailRegister.java

@@ -21,8 +21,8 @@ public class ProcessSyncEmailRegister implements SynchronousProcess {
     @Inject
     private LimboPlayerTaskManager limboPlayerTaskManager;
 
-    ProcessSyncEmailRegister() { }
-
+    ProcessSyncEmailRegister() {
+    }
 
     public void processEmailRegister(Player player) {
         final String name = player.getName().toLowerCase();