Renamed StatusObervable to StatusCallback.
Added method messageCallback for messages, warnings, errors.
Moved GeomUtils::createFace, GeomUtils::extrude, GeomUtils::sweep to new class Sweeper.

git-svn-id: http://ifcplusplus.googlecode.com/svn/trunk@34 315f8137-1bae-fbf7-f064-ab920df865c0
IfcPPModel is now derived from StatusCallback, so that it can send messages of different severity levels (minor warning, warning, error, general message) instead of just throwing exceptions.
Renamed IfcPPEntity::unlinkSelf to IfcPPEntity::unlinkFromInverseCounterparts

git-svn-id: http://ifcplusplus.googlecode.com/svn/trunk@35 315f8137-1bae-fbf7-f064-ab920df865c0
git-svn-id: http://ifcplusplus.googlecode.com/svn/trunk@36 315f8137-1bae-fbf7-f064-ab920df865c0
git-svn-id: http://ifcplusplus.googlecode.com/svn/trunk@37 315f8137-1bae-fbf7-f064-ab920df865c0
unified StatusCallback::progressCallback and StatusCallback::messageCallback.
messageCallback has now different message types, including progress (for example to update the progress bar in gui)

git-svn-id: http://ifcplusplus.googlecode.com/svn/trunk@38 315f8137-1bae-fbf7-f064-ab920df865c0
git-svn-id: http://ifcplusplus.googlecode.com/svn/trunk@39 315f8137-1bae-fbf7-f064-ab920df865c0