QGIS project indicates wrong layer SRSs when != WGS 84

[das-g]

The QGIS project included in the GIS exports declares all layers being WGS 84 (EPSG:4326), even when they aren't (because a different coordinate system has been chosen.)

[das-g]

There's three ways to solve this:

1. Don't include QGIS projects when a SRS other than WGS 84 has been chosen.
   or
2. Create data for all offered SRS, reference it from a new QGIS project each, then see what the content of the <srs> element in the project file is (a lot of manual work with all the UTM zones we offer!) and hard-code that mapping in OSMaxx and/or figure out the pattern and implement it.
3. Find out how QGIS determines this data (see gis.SE question How can I create a consistent element in a QGIS project's layer?), then imitate that in OSMaxx.

Suggestion: Do (1) now as a workaround. Then wait for the gis.SE question to be answered to see whether we can do (3). If not, fall back to (2).

@sfkeller, @hixi what do you think?