Modify API handler generator to support plural names

This patch fixes the decorator for the API handler generator to add
get_resources with the appropriate pluralized name.

Change-Id: Ifffbb8f70390b9f543b0e267e681b86b9508432c
Signed-off-by: Taku Fukushima <tfukushima@midokura.com>
Add Tunnel Zone and Tunnel Zone Host API handlers

This patch adds TunnelzoneHandlerMixin and
TunnelzonehostHandlerMixin to the core plugin using
generate_methods decorators.

This patch also adds symbols for 'list', 'show', 'create', 'update'
and 'delete'. It'd be too easy to have typos for them and I added
symbols for them to make it easier to detect typos using the static
checker.

Change-Id: Ia652c5afa0e00a358325b80d6c6dab27152ced56
Signed-off-by: Taku Fukushima <tfukushima@midokura.com>
Add tunnelzone extension

This patch adds tunnelzone extension and unit tests for tunnelzone
extension.

Change-Id: I085977e56928003e0421b1f210386fec8731a493
Signed-off-by: Taku Fukushima <tfukushima@midokura.com>
Add methods required for the plugin

Change-Id: Ifca07bf17ac9c7e946101ff665f3aef310949e30
Signed-off-by: Taku Fukushima <tfukushima@midokura.com>