Location Completion

### Problem

location completion is something we need to do in at least a few places:
* Adding location to a Calendar event
* Adding location to a reminder in Tasks
* Searching locations in Maps

It's fairly complicated if we want to provide consistent results with place icons and good descriptions etc

### Proposal

I think the most drop-in solution for developers would be something like a `Granite.LocationSearchEntry` that returns a `Geocode.Location`

### Prior Art (Optional)

The location search in Maps is pretty decent in terms of nice formatting location rows with colored icons etc