Add support for cracking KDE KWallet files

Test Data: https://github.com/kholia/kwalletcrack/blob/master/testdata/openwall.kwl

Usage:

```
$ hashkill --plugin kwallet -f openwall.kwl -r dictionary -a ~/dictionary

[hashkill] Version 0.3.1
[hashkill] Scheduler initialized.
[hashkill] Plugin 'kwallet' loaded successfully
[hashkill] Rule based attack, using rule:dictionary
[hashkill] File openwall.kwl loaded successfully
[hashkill] CPU features: SSE2 SSE3
[hashkill] Detected 3 CPUs.
[hashkill] Found GPU device: Advanced Micro Devices, Inc. - Cayman
[hashkill] Found GPU device: Advanced Micro Devices, Inc. - Cayman
[hashkill] Temperature threshold set to 90 degrees C
[hashkill] Spawned 3 threads.
[hashkill] Attack has O(n) complexity
[hashkill] Initialized hash bitmaps


[hashkill] -= Cracked list =-

Username: 		Hash: 					Preimage:
-----------------------------------------------------------------------------------
openwall.kwl  	KDE KWallet file                         	openwall 
```