Expose more

The idea here is to make the library more useful by exposing some of the useful things it does internally.

Services found are locked objects, since they are only ever created and never mutated. The array of services found is not shared, but the contents are in a new array through the getter.

Other major updates include:

• Hooks to see what the advertising is actually doing
• A fix to the target in the data in the SRV records to include the updated host
• Updated tests
• ondown function for the search, and an option to not start the search straight away