Group TLV refactors

Associated Meterpreter PR -> https://github.com/rapid7/meterpreter/pull/82

This PR contains the MSF side of the TLV refactors that were done after the group packet code was added. Details of that can be found in the Meterpreter PR. I wanted to add more to this but I had run out of time.

### Verification
- [ ] ADSI queries continue to function correctly (including with new structure of data coming across the wire)
- [ ] service enumeration functions correctly