v0.57

Main change is the introduction of a community feed. See vessels received by nearby stations in your webviewer. Feed the aiscatcher.org server by running with -X and enable a map layer in the webviewer with nearby vessels from a return feed.

Other changes:

• Performance improvements when drawing a large number of vessels by switching from Leaflet to Openlayers (notice this might require re-working some plugins). In openlayers it is more straightforward to plot ship icons on the canvas.
• option f that writes the NMEA lines to a specified file
• smaller default icons and setting option to set icon size
• setting option to define width of vesseltracks
• performance improvements for TCP input and UDP output
• Option to auto terminate the program if no messages received for a while, e.g. after 10 minutes -T 600 nomsg_ony. This will help cure network connections for input or devices going stale without an error