Merge pull request #138 from andrew-elder/staging

lib: controller: function end_station_imp *at(size_t i) now uses lock_guard
cmd_line: view details command now operates on selected configuration
Merge pull request #142 from vronchetti/issue_109

Issue 109
Merge branch 'staging' of https://github.com/audioscience/avdecc-lib into vr-counters