Credential Gem: Post/Windows/Gather - credential_collector

This is a refactor of 'post/windows/gather/credentials/credential_collector.rb'  to support the Metasploit Credential gem as part of Loginpalooza.

**Verification**

- [ ] Verify that the database is connected
- [ ] Establish Meterpreter on Windows target running in context of target's platform and SYSTEM
- [ ] ````use post/windows/gather/credentials/credential_collector````
- [ ] ````set SESSION <session_id_of_meterp_above>````
- [ ] ````run````
     - [ ]  Results including password hashes should be printed to console
- [ ]  ````creds````
- [ ]  __VERIFY__ that hash information in the 'Collected hashes..' section of the console output is listed correctly in the output of ````creds````


My testing was performed using 'exploit/windows/smb/psexec' with 'windows/meterpreter/reverse_https' against Windows 2008 R2 and Windows 2012 R2.
I believe this should be `self.refname`