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**

- [x] Verify that the database is connected
- [x] Establish Meterpreter on Windows target running in context of target's platform and SYSTEM
- [x] ````use post/windows/gather/credentials/credential_collector````
- [x] ````set SESSION <session_id_of_meterp_above>````
- [x] ````run````
     - [x]  Results including password hashes should be printed to console
- [x]  ````creds````
- [x]  __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.