[Patch {in progress, awaiting feedback}] Autofilter: extract numeric value from number+unit

[simon04]

In order to make incline=42% and maxspeed=42 mph work, we have to somehow extract the numeric value from those tags.

I propose the following procedure given in pseudocode for a primitive osm and value (42%) for key (incline):

intValue = rule.valueExtractor(value) || rule.extractDefaultValues(osm)
filter = filter(key, intValue)
label = rule.valueFormatter(intValue)
button = button(label)

[simon04]

The patch is not yet finished; of course, the unit tests need to be adapted/extended.

[simon04]

In 15838/josm:

fix #18679 - Autofilter: extract numeric value from number+unit

[simon04]

In 15839/josm:

see #18679 - Autofilter: refactoring