Major refactoring with unusable middle steps -> no commit earlier...
This compiles but only the KSaneDevice works somehow not KSaneWidget.

Changes:
- Remove the namespace KSaneIface and make sure all classes start with KSane as
they mostly have done already.

- Remove the creategui() function KSaneOption -> gui-less
- Rename Class files to the same name to simplify #include "..."
- Rename header protections to be the Class name + "_h" for easier class renames
- Rework authentication and sane access (only one sane_init() / process)
- Replace float with qreal
- And more...