Fix broken i18n support

In notification and publisher.rpc module, there are some log messages
don't support i18n, this patch fixes them.

NOTE: rename unused variable from _ to n, because it will overshadow
global _ of gettext.

Change-Id: Ic703fe6536234f4d51a84f4a3b2e04049ec6f3b5
Closes-Bug: #1263711
requirements: drop netaddr

We don't use directly, so there is no need to require it.

Change-Id: I94bbe7fbcfe192ca355ad00a64e0720addc1bb10
Remove redundant meter (name,type,unit) tuples from Resource model

Fixes bug 1267162

Previously, a list of meter (name,type,unit) tuples with per-sample
cardinality was added to the Resource model by the storage driver
get_resource method.

However this potential huge and highly repetitive list was then
promptly discarded by the API layer, as the meter links in the API
Resource representation are populated via subsequent calls into
the storage driver get_meters method.

Now, we avoid the scaling issue by suppressing the creation of
this unused meter list.

Change-Id: I18dee7552836c724798ea1340e2e933c09d8a294
Merge "Remove redundant meter (name,type,unit) tuples from Resource model"
Merge "Fix broken i18n support"
Merge "requirements: drop netaddr"
Added resources support in pollster's interface

1. Change the pollster's interface to support resources:
- Added optional parameter 'resources' to the method get_samples. It
  specifies a list of the endpoints from which the pollster would get
  data.

2. Change the PollingTask to record the resources for each pollster.

3. Pass the resources recorded in PollingTask to the pollsters in
central agent.

This patch only changes the interface of pollsters and PollingTask in
central agent. The existing central agent's pollsters still ignore the
resources passed in by the PollingTask.

Implements: blueprint support-resources-pipeline-item
Change-Id: Ic7a83c63ea291d0527004113bc8d8bb09311d14f
Add resource loader support

Added the resource loader interface and base classes, also the
FileResourceLoader implementation to load the resources from a YAML
file.

The new method ceilometer.resourceloader.get_resources() can find the
appropriate resource loader and use that loader to load the resources to
return.

e.g: Suppose we have a YAML file /foo/bar with the following content:

- snmp://1.1.1.1
- snmp://2.2.2.2

and for the foloowing pipeline resource definition:

resources:
    - fileloader:///foo/bar
    - ipmi://1.2.3.4

The get_resources() will use the FileResourceLoader to load the
resources from the file /foo/bar. For the other resource
'ipmi://1.2.3.4', because no mapping resource loader can be found,
it will assume it's the actual resource to be return. So the returned
list of get_resources() is: ['snmp://1.1.1.1', 'snmp://2.2.2.2',
'ipmi://1.2.3.4'].

Implements: blueprint support-resources-pipeline-item
Change-Id: I438ecabdcfae0a03fa89d150d31dc9fbb3aeda1f
Ganglia Pollster

new : one pollster to many metrics

reuse pipeline concept but change the logic
new pollster type : multi-meter
and break the logic of pipeline shared acrosse all pollsters.
Each pollster have a pipeline
use meters defined in pipeline(s) file to filter metrics fetched.

Todo :
* unittest
* doc

imlements bp applications-metrics-from-instances

Change-Id: I0fdd6691a22d715d573c1086d1a5df1827855167