Add button to delete all local OSM edits

[ypid]

As I like to edit the Changeset with JOSM before I upload it to OSM it would be nice if OsmAnd would offer a way to delete all local edits afterwards.

I usually export them to the file poi_modification.osc, load them in JSOM, edit them and finally upload my changes. After that I have to delete every single POI in OsmAnd manually to not get the same POI that I already uploaded next time again.

[vshcherb]

We don't support issues on github. But that functionality must be already in night builds, you could try it out.