Do slightly more validation if NMSettingVlan properties, and make sure
that at least one method of specifying a parent is used.
Remove the check that id is in range, since gobject will not allow you
to set the property to a value outside its declared range anyway.
Add documentation so the API spec generator can do something
for the VLAN setting. Also enforce validation of the ingress
and egress priority maps; 802.1D priorities are limited to
values from 0 - 7 and Linux SKB values are 32 bits.
Also, the 'slave' property is a duplicate of the 'master'
property added to NMSettingConnection in the bonding work
so we can get rid of it and use 'master' instead.
