Improve layer naming

[SlowMo24]

Layers are currently named 'ohsome_MM-DD-YY:hh-mm-ss enpoint_type' . ISO time format would be a better choice, currently the meaning of these numbers is a bit of a riddle.

[SlowMo24]

Also if the response contains multiple geometry types, the plugin will create multiple layers which could be prepended with the respective type (although the geom-type is visible from the UI through the icon).