Code review comment for lp:~frankban/juju-quickstart/old-style-bundles-regression

*** Submitted:

Fix the old-style bundle regression.

This branch fixes
https://bugs.launchpad.net/juju-quickstart/+bug/1429129
In essence, legacy bundles are converted by the
ingestion process like the following:
- if a basked includes multiple bundles, the resulting
   v4 bundle name is {basket-name}-{bundle-name} for
   each {bundle-name};
- if a basket only includes one bundle, the v4 bundle
   is just {basket-name}.
Previously quickstart always assumed the former: this
branch adds a check for the latter before exiting with
an error.

This branch also introduces a charmstore module in
quickstart. All the interactions between quickstart
and the charm store are now collected in this module.

As part of this refactoring, quickstart is now able
to distinguish HTTP 404 errors and all the other
generic IOErrors that can be raised when connecting
to the network.

Also simplified the logging format and bootstrap logging
earlier in the application execution.

Tests: `make check`.

QA:
install bundles with quickstart:
`devenv/bin/juju-quickstart {bundle}`
Try the following bundles:
- devenv/bin/juju-quickstart mediawiki-single
- devenv/bin/juju-quickstart u/bigdata-dev/apache-analytics-sql
- devenv/bin/juju-quickstart bundle:mediawiki/scalable
- devenv/bin/juju-quickstart
bundle:~landscape/landscape-dense-maas/landscape-dense-maas
- devenv/bin/juju-quickstart bundle:django/example-single

Those instead should return errors:
- devenv/bin/juju-quickstart mediawiki/trusty
- devenv/bin/juju-quickstart mediawiki-nosuch
- devenv/bin/juju-quickstart no-such
- devenv/bin/juju-quickstart bundle:no/such
- devenv/bin/juju-quickstart bundle:invalid
- devenv/bin/juju-quickstart
bundle:~landscape/landscape-dense-maas/landscape

R=jeff.pihach, rharding, bac
CC=
https://codereview.appspot.com/215070043

https://codereview.appspot.com/215070043/