Add reference checking for module_reference.rb

This adds a new reference checking feature to the module_reference.rb utility. It's for:
https://github.com/rapid7/metasploit-framework/issues/4039

## Verification 1

- [ ] Do ```./module_reference.rb -f auxiliary```
- [ ] Make sure you only see references from auxiliary modules

## Verification 2

- [ ] Do ```./module_reference.rb -c -o /tmp/ref.txt -f auxiliary```
- [ ] Make sure it checks the references. Alive means the reference is good. Down means the reference is down. Unsupported means the reference ID is invalid.
- [ ] Make sure there's a copy of the results in /tmp/ref.txt

## Important

Try not to run ```./module_reference.rb -c -f All```. It will take all day to go through 6600+ references.