This patch saves the webchat conversations messages in the browser's
local storage. When the user comes back to the page, the
conversations are restored.
This patch makes use of the gps settings in the webchat section.
If the user sets the latitude and longitude in the config file, then
the gps beacon button will be enabled. The gps button will still be
enabled if the http connection is over SSL.
This patchset allow getting the GPS coordinates from the browser's
geolocation API (which can be denied by user), then send's the GPS
coordinates to aprsd via socketio and then aprsd sends a beacon.
This allows the APRS network to know the location of the person running
the webchat app via browser so packets can get routed back to it.