id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc
8687	Warn about letters in number only values	skyper	team	"Looking at the values for `height` on [http://taginfo.openstreetmap.org/keys/height#values taginfo], I find a lot of values containing not only numbers but unneeded letters.

There are some tags which only accept numbers as value or not more than some letter combinations:
* layer
* level
* height
* (max)height*
* minclearance
* width
* (max)width
* max-/mintrackwidth
* maxspeed*
* voltage
* frequency
* gauge
and probably some more.

A warning if the value does not only contain a valid number would be nice. Probably needs to categories:
1. a warning about letters 
2. a warning about wrong decimal separator (e.g. `,` or `:`)

r5935
"	enhancement	closed	normal	14.01	Core validator		fixed	number value warning	RicoZ