Implemented base + moved plugins & service conf

In this changeset, I implemented the main logic although this is
mainly a shameful copy/paste of Nova's blueprint
https://blueprints.launchpad.net/nova/+spec/centralize-config-options

Partially Implements: blueprint centralise-config-opts

Change-Id: Ib645ad5da5c706336bb6ac37e85b027d05665c32

watcher/conf/__init__.py

@@ -0,0 +1,25 @@
+# -*- encoding: utf-8 -*-
+# Copyright (c) 2016 b<>com
+#
+# Authors: Vincent FRANCOISE <vincent.francoise@b-com.com>
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
+# implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from oslo_config import cfg
+
+from watcher.conf import service
+
+CONF = cfg.CONF
+
+service.register_opts(CONF)