Loading data on ProcessingData would lead to incomplete information
about source code locations. Rebuilding the whole model on any kind
of changed() signal is wasteful.

Task-number: QTCREATORBUG-11100
Change-Id: I9f8d718bff6149ca2dc2d0482c11d66d940af15d
Reviewed-by: Kai Koehne <kai.koehne@digia.com>