Parse OSM XML files for changeset tags

[tsmock]

OSM xml files can look like this:

<?xml version='1.0' encoding='UTF-8'?>
<osm version='0.6' generator='JOSM'>
  <changeset>
    <tag k="additionalTag" v="Additional Tag Comment"/>
    <tag k="comment" v="Some Random Comment"/>
    <tag k="source" v="Some Random Source"/>
  </changeset>
  <OSM DATA/>
</osm>

When an OSM xml file is uploaded with this data, the tasking manager should ask if the following fields should be overridden:

1. comment (remote control variable changeset_comment)
2. source (remote control variable changeset_source)

It should also ask if the additional tags should be imported into JOSM (not currently supported by JOSM remote control, see https://josm.openstreetmap.de/ticket/18038 )

For JOSM discussions, see https://josm.openstreetmap.de/ticket/9387 and https://josm.openstreetmap.de/ticket/9472.

For JOSM remote control commands, see https://josm.openstreetmap.de/wiki/Help/RemoteControlCommands .