Offer smaller radius sizes for custom locations

[windmueller]

Describe the feature The definition of custom locations is a unique feature I really like. However, the default lowest radius of 1km is too large. One of the most common locations would be "Home" and here 200m are enough to catch minor glitches of the GPS.

That said, it would be nice if the radius slider would support a lower radius. Adding it manually with "0.2km" already works.