[Qgis-developer] Merging of revision upgrade branch

[Magnus Homann]

My 'branch' handling reading older project files is ready for merging. 
Small branch, changes basivally limimted to core/qgsproject.cpp and adds
some files to that. After mergin, all developers that have made changes 
in project file layout can starta thinking of how to handle old project 
files.

If no objections, I will merge tonight (in about 12 hours). It should be 
easily reversible if need be.

Magnus