Created standalone module for cpassword AES decrypt

There's times where you may not have a meterpreter shell to run GPP and need to just decrypt the CPASSWORD encrypted string manually. Added this modified gpp that just takes in the CPASSWORD string to decrypt and present it back. 

Output below:
```
msf auxiliary(gpp_standalone) > show options

Module options (auxiliary/gather/gpp_standalone):

   Name       Current Setting  Required  Description
   ----       ---------------  --------  -----------
   CPASSWORD                   yes       The encrypted string to decrypt.

msf auxiliary(gpp_standalone) > set CPASSWORD <encrypted_cpassword>
CPASSWORD => <encrypted_cpassword>
msf auxiliary(gpp_standalone) > exploit

[*] The decrypted AES password is: DecryptedPassword!
[*] Auxiliary module execution completed
```