Changed addresses to reflect new domain openambit.org
Log most likely reason why device cannot be opened.  Re #26

Device communication requires read/write access permissions no matter
how you look at it.  Looking at the innards of `hid_open()` shows that
that function calls `open()` with the same flags as well.
Add call to `close()` to match `open()` introduced in 4799eab
Make version comparison readable

This also fixes an endian issue with the comparison of the last two
bytes.  According to the logging output, these bytes are in little
endian order so the last byte is more significant in the comparison.
Rename `'s/supported_device/known_device/g'`

An `ambit_supported_device_t` with a `supported` value of `false` is
confusing at best.
Export clock's support status in `ambit_device_info_t`

This allows for dropping the `ambit_known_device_t` pointer from
`ambit_object_t`.
Fix log message
Add API stubs to enumerate and create clock related objects
Partially unstub newly added API

Device enumeration now relies exclusively on `udev` API.
Populate `ambit_device_info_t` fields using `udev` API
Attempt to fill in fields with firmware information

Firmware name and serial number are preferred over `udev` information
if different.  Failure to get firmware information is *not* fatal when
populating of device info fields.
Unstub `libambit_new()`
Unstub `libambit_new_from_devname()`
Unstub `libambit_new_from_syspath()`
Reimplement GUI device detection with new API
Display access error message rather than support status

If we could not access the device, there is no knowing whether the
clock is supported.  Users need to address the access error first.
Make example application use new libambit API

Device information, access issues and support status are logged to
standard output before anything else.
Drop old device detection API
Drop obsoleted `libambit` API
Drop obsoleted `ambit_object_t` fields