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/datasource/converter/CrazyLoginConverter.java

@@ -43,20 +43,7 @@ public class CrazyLoginConverter implements Converter {
         try (BufferedReader users = new BufferedReader(new FileReader(source))) {
             while ((line = users.readLine()) != null) {
                 if (line.contains("|")) {
-                    String[] args = line.split("\\|");
-                    if (args.length < 2 || "name".equalsIgnoreCase(args[0])) {
-                        continue;
-                    }
-                    String playerName = args[0];
-                    String password = args[1];
-                    if (password != null) {
-                        PlayerAuth auth = PlayerAuth.builder()
-                            .name(playerName.toLowerCase())
-                            .realName(playerName)
-                            .password(password, null)
-                            .build();
-                        database.saveAuth(auth);
-                    }
+                    migrateAccount(line);
                 }
             }
             ConsoleLogger.info("CrazyLogin database has been imported correctly");
@@ -66,4 +53,26 @@ public class CrazyLoginConverter implements Converter {
         }
     }
 
+    /**
+     * Moves an account from CrazyLogin to the AuthMe database.
+     *
+     * @param line line read from the CrazyLogin file (one account)
+     */
+    private void migrateAccount(String line) {
+        String[] args = line.split("\\|");
+        if (args.length < 2 || "name".equalsIgnoreCase(args[0])) {
+            return;
+        }
+        String playerName = args[0];
+        String password = args[1];
+        if (password != null) {
+            PlayerAuth auth = PlayerAuth.builder()
+                .name(playerName.toLowerCase())
+                .realName(playerName)
+                .password(password, null)
+                .build();
+            database.saveAuth(auth);
+        }
+    }
+
 }