Provide a result map legend (colour key)

[stefanb]

The processing results are presented on the overview maps, eg on http://results.openaddresses.io/sets/400144/ with a detail:

There are 5 colours used:

• grey (assuming no source)
• 2 shades of green (assuming ok)
• 2 shades of red (assuming some error)

On http://results.openaddresses.io/ the map: is using only 3 colours:

• grey (assuming no source)
• 2 shades of green (assuming ok)

None of the map contains an explanation what each colour means.

[daynebatten]

Could we at least get a comment here in the issue on what the colors mean? Would be nice to know, even if the pages aren't altered.

Thanks!

[iandees]

Green means downloaded successfully. Light green means a source that is large like a state or country. Dark green means a smaller entity like a city or county.

Red means an error was encountered while downloading. The dark/light variations mean the same thing as in the green case.