added vlan name allocator

Signed-off-by: Jan Dvořák <mordae@anilinux.org>
reserve more space for netdev names

10^7 is much more space to prevent collisions, especially for vxlan
interfaces that are going to be reconfigured relatively frequently.

Signed-off-by: Jan Dvořák <mordae@anilinux.org>
restructure managers to support transactions

Instead of applying changes one-by-one, changes are now received in
batches and managers get notified when the batch ends.

Since Sparkle does not guarantee consistency of configuration across
transaction boundaries, new tasks may not be started until the whole
batch have been processed.

Signed-off-by: Jan Dvořák <mordae@anilinux.org>