Render other types of signals

[wolfy1339]

It would be nice if the map could show all signals, even if the signal type is unknown

An example would be node/11902161621
I would expect a simple generic signal head to render if there isn't a schema style defined.

Using the generic tagging scheme as defined in https://wiki.openstreetmap.org/wiki/Tag:railway=signal?uselang=en

[hiddewie]

Good idea!