Removed libxml2 to use pugixml.
Fixed a bug with the progress bar.
Changed some things in most xml files that pugixml did not like.
Updated the Visual Studio project.
Any NULL symbol has been changed to nullptr.
This most probably broke the CMake that was recently added.
And probably some other things.
Also fixed some crashbugs when the type of an item varied when you
performed a map conversion. (The item would be static_cast when copied,
which would crash if the type had changed).
Clean git repository since the old svn / git mess was pretty much
unrecoverable unfortunetly. I would have liked to keep the history
for posterity, but that proved to be a futile quest.
