Use metrics-lib's getHidserv* methods in Metrics' hidserv module
When Metrics' hidserv module was written in March 2015, metrics-lib did not support hidserv-* lines in extra-info descriptors, so it had to implement its own parsing code and parse extra-info descriptors a second time.
This has changed in December 2015 with metrics-lib 1.1.0 adding "support for hidden-service statistics in extra-info descriptors".
It's time to replace that custom parsing code in Metrics' hidserv module and use the methods provided by metrics-lib.