This plugin supports multiple plugins at same time. This plugin is for L3 connectivility
between networks which are realized by different plugins. This plugin add new attribute 'flavor:id'.
flavor:id correspond to specific plugin. flavor-plugin mapping could be configureable by plugin_list config.
This plugin also support extensions. We can map extension to plugin by using extension_map config.
Implements blueprint metaplugin
Change-Id: Ia94d2349fb3ce9f121bbd2505324ae6f0c34247a
b1fa5ef2ca