repeaterbook: use a distict user agent

Also display the errors on console when the JSON cannot be decoded.

Merge pull request #89 from mycodeplug/seattledmr-fallback

SeattleDMR fallback: use a cached copy

Merge pull request #87 from jancona/bogus-frequency

Ignore non-amateur frequency from Repeaterbook (instead of failing)

Merge pull request #86 from masenf/farnsworth-contact-dedupe

Farnsworth contact dedupe

Merge pull request #83 from masenf/new-pnwd-url

dzcb.pnwdigital: update DigitalRepeaters zip link

Merge pull request #82 from masenf/cache-repeaters

dzcb.pnwdigital: provide fallback for PNWDigital repeaters

Merge pull request #81 from masenf/uniquify-zones

Uniquify zone names (and warn about it)

Merge pull request #79 from masenf/ignore-bogus-coords

repeaterbook: skip records with invalid coordinates

Merge pull request #77 from masenf/allow-invalid-tone

Allow invalid tone

Merge pull request #74 from masenf/beta-docs

Beta Documentation