ifconfig: functions for tunnel creation and manipulation

Create, change and delete sit, ipip and gre tunnels.
sit: dbus factory service

Also contains service functions for changing and deleting sit tunnel.
ipip: dbus factory service

Also contains service functions for changing and deleting ipip tunnels.
gre: dbus factory service

Also contains service functions for changing and deleting gre tunnels.
client: add support for parsing general tunnel attributes

Needed for sit, ipip and gre tunnels.
client: parse tunnel ifcfg files and generate xml configs
client: extend hwaddr print in ifstatus

Use local-address and remote-address in place of hwaddr/hwpeer for
sip, ipip and gre tunnels.
Merge pull request #381 from kmroz/tunnel-digger-3
Merge pull request #380 from mtomaschewski/master-defer-lease
ipv6: wait for addresses to become usable (bnc#882259)

Added a temporary applying lease state, which is used while
applying a new granted lease to the system.

When a granted ipv6 lease arrives and the addresses are set,
we've to wait unti the kernel verifyed them for duplicates
and removes the tentative flag before we continue to apply
the rest of the lease and finally inform the client about.

When the kernel detects duplicates, the state changes either
to failed and we do not set further settings or to requesting
state for dhcpv6 leases as it automatically declines.
Merge branch 'master' into testing
Merge pull request #381 from mtomaschewski/ipv6-tentative-1