[PATCH] Allow DataSet merges without merging the Bounds

[taylor.smock]

This is a step towards fixing #8082. Since this patch allows us to avoid adding bounds to an area (and giving the user and JOSM the wrong idea about the area being fully downloaded), I should be able to write a patch that uses Overpass to download an area around the node/way without also adding it to the bounds of the DataSet.

I just need to come up with a way to download the parent way(s) and the parent relation(s) without getting a lot more data than is needed.

[taylor.smock]

Overload the DataSet.merge() method to have another variable about whether or not the DataSet bounds should be merged. This should probably only ever be used when downloading with Overpass without the user entering in the query themselves.

[Don-vip]

In 15127/josm:

fix #17724 - Allow DataSet merges without merging the Bounds (patch by taylor.smock)