Add timestamp to lift status

Data timestamp (in millis) is a time of last successull status
retrieval.
Timestamp is now rendered as a part of resort section. It is also
returned by resort API.
Display 'next update' indicator for each resort

Update data every 60 seconds
Update indicator every 5 seconds
Just as before opening a resorts updates it immediately
Merge branch 'update-time'
Release 1.7.0