Add SystemVendor and SystemModel string properties to the main interface

This functonality allows colord-kde, gnome-settings-daemon and xiccd to drop the
manual DMI parsing and it also allows us to sanitize the vendor string so that
it looks in the same style as the EDID-derived value.
Allow the user to specify a non-qualified path when using FindProfileByFilename

This allows the user to call FindProfileByFilename('Bluish.icc') rather than
specify the full file path and is required for the ucmm-shim used by Argyllcms.
trivial: Add another python example that shows getting a refcounted list
trivial: Update TODO to reflect reality
trivial: Fix typo in debug message
trivial: Remove some dead code

Our GLib dep is 2.32.0 now.
Release colord 1.0.2