Move wire format to separate package.
Wireformat for sending metrics to the collector service.
Merge pull request #1050 from tasdomas/metrics-wire-format

Metrics wire format

Metrics wire format defines the format that will be used to send metrics to and receive responses from a metrics collector service.
Add support for using index2.json for tools
A few formatting tweaks
Merge pull request #1060 from wallyworld/simplestreams-index2

Add support for using index2.json for tools

Fixes: https://bugs.launchpad.net/juju-core/+bug/1389807

With this change, when loading tools metadata, firstly we look for an index2.json file.
If that's not there, we look for index.json

This allows extra metadata to be added for use by 1.21 and later versions of Juju, and 1.20 and ealrier will not be affected.

The metadata generation plugins have been changed to generate index2.json

As a drive by, some old code, no user used since provider storage was dropped, was deleted.