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.
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.
A static symbol Slic3r::SEMVER is introduced, which holds
the running slicer's Semver object.
This is mainly done to make testing updater behaviour
_much_ easier. Additionaly to cleanup some questionable code
(Semver was being parsed multiple times / in multiple places
in the frontend.)
