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.
fix(coreos): remove refs to obsolete update-engine-reboot-manager

This was removed from CoreOS a while ago, so our unit file was having
no effect.
https://github.com/coreos/update_engine/pull/28
fix(contrib/ec2): add json extension to cloudformation template

The CloudFormation Template has a .template extension although its a json file.
This makes it difficult to parse/edit it as editors dont recognize it as JSON file.
So added the .json extension behind its name and also updated gen-json.py which
uses it.
fix(contrib/ec2): add script to update the CloudFormation
fix(controller/procfiie): Removed Procfile as its not used anywhere
Merge pull request #1308 from developerinlondon/fix/remove-procfile-from-controller

fix(controller/procfiie): Removed Procfile as its not used anywhere
Merge pull request #1304 from developerinlondon/fix/add-json-extension-to-cloudformation-template

fix(contrib/ec2): add json extension to cloudformation template
Merge pull request #1302 from ddollar/ec2-cloudformation-update

fix(contrib/ec2): add script to update the CloudFormation
fix(tests): increase component test timeouts to 20min

Most component test failures in our CI system recently have been due
to the tests taking longer than the default Go testing package timeout
of 10 minutes. The tests are in progress, but Go kills the process
after 10 minutes and reports it as failed.

The tradeoff here is that if one of the tests is actually stuck,
we wait twice as long to find that out, but overall this seems like a
fix for CI stability. Builder was increased to 30m since it takes much
longer to pull slugbuilder.
Merge pull request #1316 from deis/component-test-timeouts

fix(tests): increase component test timeouts to 20min
Merge pull request #1152 from deis/remove-update-reboot

fix(coreos): remove refs to obsolete update-engine-reboot-manager
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