API consumers should fetch the persistent data when they are done and
store it to disk. It is undefined when this data is updated by the
driver, but in general, it should only be updated once the first time
a device is used.
We can avoid having multiple device feature-check functions now and
just rely on a few.
Add uncrustify config to properly handle begin/end deprecation macros.
It can be convenient for device users to check what it supports, without
having multiple functions to check each single feature.
So expose this and add tests.
Use the virtual image device as base for now, while the new setup allows
to create easily fake device drivers without including the driver in
libfprint itself and test all the fpi_device functionalities.
