[WIP] Satellite Pollster to collect PaaS metrics

The pollster is designed to run in instance (but can be used to monitor
infrastructure server)

This patch provide implementation with Ganglia (Gmond and Gmetad)
The Ganglia pollster is able to forward metrics to ceiloemeter API
from one host or from many cluster (group of hosts)
depending of Ganglia deployment.

It use pipeline concept (transformers, resources, publishers)
but change the logic "one pollster == one meter"
by "one pollster == many metrics"

Introduce a new HTTP publisher : the circle is closed.

A sattelite pollster give to user the possibilty to fetch
and filter metrics from "resources" and publish them  through pipeline(s).

Basically, the manager of the pollster follow this logic :
Create a timer (worker thread) for each different intervals (same as
now).
if 2 pipelines have different intervals OR differents resources,
pollster will be run twice in separate thread (syncrhonized)
with his correspondant publisher context.
if 2 pipelines have same intervals AND same resource(s), pollster
will be run once with all pipelines chained.

Todo :
* approuval
* unittest
* doc

Future:
* filtering metrics by regexp (ie gpu[0-9]_cpu)
* transformer : mean of of all r'gpu[0-9]_cpu'

imlements bp applications-metrics-from-instances

Change-Id: I0fdd6691a22d715d573c1086d1a5df1827855167