WMIC Post Mixin

This starts to utilize the ExtAPI clipboard functionality to retrieve WMI results. Something that was previously required file IO as WMIC does funny things with its stdout. N.B. Using the clipboard as output does not capture ERROR conditions so we cant see why it has failed but know it has if we get no text back at all. 

The Local WMI module is now slightly more responsive as it can detect a successful command and skip a host if the command fails.

The post/windows/gather/wmic_command can now target another host with credentials or using the current user's credentials. 

The shadowcopy mixin seems a bit inefficient, instead of doing a list for all the values and doing some parsing in ruby it individually grabs them one by one - which is quite slow for vss_list...

## Verification
- [x] post/windows/gather/wmic_command can run a single WMI query
- [x] post/windows/gather/wmic_command can run multiple queries from a resource file
- [x] post/windows/gather/wmic_command can run a remote query
- [x] Output of above is correctly stored in loot file
- [x] exploit/windows/local/wmi returns shells on multiple hosts
- [x] exploit/windows/local/wmi will skip a host on error (e.g. Incorrect credentials/Firewall)
- [ ] post/windows/manage/vss_create works
- [ ] post/windows/manage/vss_list works
- [ ] post/windows/manage/vss_mount works
- [ ] post/windows/manage/vss_set_storage works
- [ ] post/windows/manage/vss_storage works
- [ ] exploit/windows/local/vss_persistence works