lib/quantum: refactor quantum plugins and third party

As quantum plugin support is coming like floodlight, nvp and nec,
it's worth while to refactor quantum plugin logic so that each plugin can
be modified/enhanced intervening with other quantum plugin.
And new plugin support can be added easily (hopefully) without modifying
core logic.

Change-Id: Ic5ab5b993272fdd3b4e779823323777a845ee681
diff --git a/AUTHORS b/AUTHORS
index 7ec1f66..35c0a52 100644
--- a/AUTHORS
+++ b/AUTHORS
@@ -19,6 +19,7 @@
 Gary Kotton <gkotton@redhat.com>
 Hengqing Hu <hudayou@hotmail.com>
 Hua ZHANG <zhuadl@cn.ibm.com>
+Isaku Yamahata <yamahata@private.email.ne.jp>
 Jake Dahn <admin@jakedahn.com>
 James E. Blair <james.blair@rackspace.com>
 Jason Cannavale <jason.cannavale@rackspace.com>