Update provider fields.

Update provider fields.

Update the list of fields that quickstart
expects for each provider type. Also make
some OpenStack fields optional 
(use-floating-ip, tenant-name and region).

Update the links to the provider documentation
(use jujucharms.com).

Update the jujubundlelib dependency to use the
latest one.

Tests: `make check`.

QA:
- check that the environment editing in the
interactive session looks good 
(especially the openstack/azure environments
creation).
- use quickstart as usual 
(`devenv/bin/juju-quickstart`), to start 
(for instance) an ec2 or an azure environment.

https://code.launchpad.net/~frankban/juju-quickstart/optional-fields/+merge/257913

(do not edit description out of merge proposal)

[frankban, 2015-04-30 15:41:50]

Please take a look.

[frankban, 2015-05-01 07:24:57]

*** Submitted:

Update provider fields.

Update the list of fields that quickstart
expects for each provider type. Also make
some OpenStack fields optional 
(use-floating-ip, tenant-name and region).

Update the links to the provider documentation
(use jujucharms.com).

Update the jujubundlelib dependency to use the
latest one.

Tests: `make check`.

QA:
- check that the environment editing in the
interactive session looks good 
(especially the openstack/azure environments
creation).
- use quickstart as usual 
(`devenv/bin/juju-quickstart`), to start 
(for instance) an ec2 or an azure environment.

R=
CC=
https://codereview.appspot.com/234150043