fix of bug (1) - order of dialogs
fix of bug (2) - show new version dialog when triggered by user
fix of bug (3) - refresh value in preferences combobox when opening preferences
fix of bug (4) - Use fwrite instead of stream to speedup saving.
Do not show checkbox when triggered by user.
into a graph with links to the layer above / below.
In addition:
Members of LayerRegion were made private, public interface const only.
this->m_xxx replaced with just m_xxx
SurfacesPtr was made a vector of const pointers.
Most important:
Change Download dialog to select path there.
Every user query triggers new download of version file, possibly stops former download (with dialog).
Some functions refactored.
