Add skeleton of a decorator for API handler mixins

This patch adds a decorator function that generates required methods for
API handler mixins based on the given list of strings represent required
handlers.

Change-Id: I8da516c849d1216201af9e753ab9fd1fe6ce9ddb
Signed-off-by: Taku Fukushima <tfukushima@midokura.com>
Modify the core plugin to load extensions

Change-Id: Iff53db4754aac857e4dd10a2be1ade975029eb14
Signed-off-by: Taku Fukushima <tfukushima@midokura.com>
Add constants for generate_methods

This patch 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: I7e786ba0ca0e24c272ab016b3fdf25cc608a87f3
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.

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