Add "colour:back" property to the "City Limit Sign" preset

[alexey.zakharenkov]

What steps will reproduce the problem?

1. Press F3 or use "Presets" menu
2. Find "city limit" preset
3. You'll see "City Limit Sign" preset card with few fields.

What is the expected result?

Some users would be glad to see one more field, for traffic sign background colour.

Additional information.

In many countries a city limit sign may have different background colour which imposes different limitations, in particular on maxspeed.

As one can see, e.g., at ​https://en.wikipedia.org/wiki/Comparison_of_European_road_signs#Built-up_area_limits, white, blue, green, yellow, brown colours are used.

Please add "colour:back" tag with predefined extensible list of values to the "City Limit Sign" preset. "white" (about 2850 uses) and "blue" (about 370 uses) are the most popular values used with traffic_sign=city_limit tag at the moment in OSM. The Overpass Query:

[out:csv("colour:back",count)][timeout:1800];
node[traffic_sign=city_limit]["colour:back"];
for (t["colour:back"])
{
   make stat
       "colour:back"=set(t["colour:back"]),
       count=count(nodes);
   out;
}

Relative:URL: ^/trunk
Repository:UUID: 0c6e7542-c601-0410-84e7-c038aed88b3b
Last:Changed Date: 2022-05-29 21:53:52 +0200 (Sun, 29 May 2022)
Revision:18463
Build-Date:2022-05-30 01:30:57
URL:https://josm.openstreetmap.de/svn/trunk

Identification: JOSM/1.5 (18463 ru) Mac OS X 10.16
OS Build number: macOS 12.6 (21G115)
Memory Usage: 365 MB / 2048 MB (88 MB allocated, but free)
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System property sun.jnu.encoding: UTF-8
Locale info: ru_RU
Numbers with default locale: 1234567890 -> 1234567890
Dataset consistency test: No problems found