package/gerbera: bump to version 1.8.0

Also recreate config.xml by building and running Gerbera using:

```
~/buildroot/output/target/usr/bin/gerbera --create-config > package/gerbera/config.xml

```

Note, that Gerbera sets the `<home>` parameter now to the runtime user's home by
default when generating the script. This is not appropriate when running Gerbera
on an embedded Linux system as we usually do not have multiple users or even
users at all. Therefore, we set the home directory to /var/lib/gerbera`.

As this directory is not created when installing Gerbera to the target,
it is created by the start script.

Signed-off-by: Jörg Krause <joerg.krause@embedded.rocks>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>