Features:
+* add some optional flag to ReadWritePaths= and friends, that has the effect
+ that we create the dir in question when the service is started. Example:
+
+ ReadWritePaths=:/var/lib/foobar
+
* sort generated hwdb files alphabetically when we import them, so that git
diffs remain minimal (in particular: the OUI databases we import are not
sorted, and not stable)