#369 Delete Xenforo (XF) encryption algorithm

Rationale:
- Seems not to have been working since it was added to the codebase
- Seems not to correspond to the actual Xenforo password hashing (class does some sort of JSON extraction?)
- It would be easier to rewrite it from scratch if someone requests it later

src/main/java/fr/xephi/authme/security/crypts/XF.java

@@ -1,73 +0,0 @@
-package fr.xephi.authme.security.crypts;
-
-import java.security.MessageDigest;
-import java.security.NoSuchAlgorithmException;
-import java.util.ArrayList;
-import java.util.List;
-import java.util.regex.Matcher;
-import java.util.regex.Pattern;
-
-/**
- */
-public class XF implements EncryptionMethod {
-
-    @Override
-    public String computeHash(String password, String salt, String name) {
-        return getSha256(getSha256(password) + regmatch("\"salt\";.:..:\"(.*)\";.:.:\"hashFunc\"", salt));
-    }
-
-    @Override
-    public HashResult computeHash(String password, String name) {
-        String salt = generateSalt();
-        return new HashResult(computeHash(password, salt, null), salt);
-    }
-
-    public boolean comparePassword(String hash, String password, String salt, String name) {
-        return hash.equals(regmatch("\"hash\";.:..:\"(.*)\";.:.:\"salt\"", salt));
-    }
-
-    private String getSha256(String password) {
-        MessageDigest md = null;
-        try {
-            md = MessageDigest.getInstance("SHA-256");
-        } catch (NoSuchAlgorithmException e) {
-            // TODO #358: Handle exception properly
-            throw new RuntimeException(e);
-        }
-        md.update(password.getBytes());
-        byte byteData[] = md.digest();
-        StringBuilder sb = new StringBuilder();
-        for (byte element : byteData) {
-            sb.append(Integer.toString((element & 0xff) + 0x100, 16).substring(1));
-        }
-        StringBuilder hexString = new StringBuilder();
-        for (byte element : byteData) {
-            String hex = Integer.toHexString(0xff & element);
-            if (hex.length() == 1) {
-                hexString.append('0');
-            }
-            hexString.append(hex);
-        }
-        return hexString.toString();
-    }
-
-    @Override
-    public String generateSalt() {
-        // TODO #369: Find out what kind of salt format XF uses
-        return "";
-    }
-
-    @Override
-    public boolean hasSeparateSalt() {
-        return true;
-    }
-
-    private String regmatch(String pattern, String line) {
-        List<String> allMatches = new ArrayList<>();
-        Matcher m = Pattern.compile(pattern).matcher(line);
-        while (m.find()) {
-            allMatches.add(m.group(1));
-        }
-        return allMatches.get(0);
-    }
-}