Add Android gadget manufacturer and vendor id support

Signed-off-by: Philippe De Swert <philippe.deswert@jollamobile.com>
Fix bug in the conf file merging algorithm when the main config file gets removed.

mkdir will return a negative value also if the dir already exists, so we cannot
rely on it as a main test for creating the config file.

Signed-off-by: Philippe De Swert <philippe.deswert@jollamobile.com>
g_strfreev does not seem to work correctly in this context.
More investigation needed.
Also fix a comment

Signed-off-by: Philippe De Swert <philippe.deswert@jollamobile.com>
Add product key for android gadget

Signed-off-by: Philippe De Swert <philippe.deswert@jollamobile.com>