fix(controller): set default release image

If you scale an application with `deis scale cmd=1` before an
application has been pushed, it should deploy deis/helloworld.
However, the initial release (v1) does not have a image set for
the release, only the build. Setting the default to deis/helloworld
fixes the "scale before deploy" problem.
fix(client): clear cookies on login, logout, register

We should be clearing all cookies, since we can only be logged into
a single user and cluster at the same time. This fixes the 403 Forbidden
when being logged in immediately after registering.
feat(contrib): add DigitalOcean provisioner booting CoreOS via kexec

This introduces a provisioning script for Deis on DigitalOcean droplets. As DigitalOcean
does not (currently) support CoreOS, we deploy CoreOS on top of Ubuntu 14.04 using kexec
on boot to switch to the CoreOS kernel and initrd. The state filesystem is a loop
mounted btrfs.

The CoreOS bootstrapping is heavily based on Levi Aul's code:

  https://gist.github.com/tsutsu/490f35f48897df0f5173

We don't use Debian 7.0 as base distribution because kexec is unstable on the Debian
kernel.
refactor(contrib/digitalocean): clean up README, act more like other contrib/ scripts

Updates the README to flow more like the other contrib/ scripts.
Also adds a provision-do-cluster.sh
feat(contrib/ec2): launch into vpc

Modifies the cloudformation configuration to create resources within the
confines of a VPC.

fixes #1005
fix(contrib/ec2): fix launching into VPC

To successfully launch into a VPC, we must specify the availability
zones associated with each subnet.
fix(*): fix etcd_safe_set to not override values

Refactors etcd_safe_set so it doesn't overwrite custom settings.

TESTING: rebuild and restart components, setting a non-default
custom value
```console
dev $ make uninstall
dev $ vagrant rsync && make build
dev $ vagrant ssh
coreos $ etcdctl set /deis/controller/webEnabled 1
dev $ make run
```
Make sure the settings have taken effect.

Changes proposed by @aledbf

fixes #1210
fix(Dockerfile): ensure `apt-get install` is prefixed by `update`

Since Dockerfile layers are cached, having `apt-get update` as a separate
command creates the potential for a subsequent `apt-get install` to fail.
Best practices (other than "install from source") seem to be to make
both commands into a one-liner.

This PR ensures we don't `apt-get install` as its own command anywhere,
removes the installation of some packages that were already in deis/base,
and removes a redundant ENV DEBIAN_FRONTEND statement.
feat(controller/coreos.py) Adding TimeoutStartSec to log and announce services

Sometimes log and announce services fail to start because they depend
on the main service, but if it takes too long they fail because of
timeout. This commit just adds the same timeout to log and announce
services than the main service has.
Merge pull request #1249 from deis/dockerfile-apt-get-fix

fix(Dockerfile): ensure `apt-get install` is prefixed by `update`
fix(confd): services check for valid config before reloading
Merge pull request #1112 from deis/check-configs

fix(confd): services check for valid config before reloading
chore(controller): update Django to 1.6.5 security release

https://www.djangoproject.com/weblog/2014/may/14/security-releases-issued/
chore(controller): update South to 1.0 final release

http://south.readthedocs.org/en/latest/releasenotes/1.0.html
Merge pull request #1248 from deis/update-django-and-south

chore(controller): update django and south
fix(controller): ignore KeyError when purging user from etcd
chore(contrib/digitalocean): make NYC2 the default region
fix(controller/registry): add old config vars

In child images, we weren't dumping the old config variables from
previous images. This would fester and would run into issues such as
environment variables going missing. Adding them back solves this issue.
Merge pull request #1332 from deis/fix-auth-cancel

fix(controller): ignore KeyError when purging user from etcd
documentation(README): add note about ram usage and Ubuntu

These fixes are to document some of the vices that have plagued me as I
was getting up to speed with Deis and its Vagrant workflow inside Ubuntu.