Stanford only: move tmp dir from edx-west/tmp to edx-west/ec2_cache

Per feedback from @feanil on PR #849, want our release branch to line up
with what we're pulling into master.

Going back to putting ssh connections in /tmp.  They have globally
unique names, putting in /tmp is consisten with other things, and having
them live in a dir named ec2_cache feels odd now.

skeleton role for db-grader-proxy

We need to refactor and clean up the user stuff.

Gugelhupf Release 2014-02-11

Conflicts:
	playbooks/ansible.cfg
	playbooks/edx-west/README.md
	playbooks/edx-west/cme-prod-app.yml
	playbooks/edx-west/prod-app.yml
	playbooks/edx-west/stage-app.yml
	playbooks/roles/datadog/tasks/main.yml
	playbooks/roles/edxapp/defaults/main.yml
	playbooks/roles/edxapp/handlers/main.yml
	playbooks/roles/edxapp/tasks/deploy.yml
	playbooks/roles/edxapp/tasks/main.yml
	playbooks/roles/edxapp/tasks/python_sandbox_env.yml
	playbooks/roles/edxapp/tasks/service_variant_config.yml
	playbooks/roles/edxapp/templates/lms-preview.conf.j2
	playbooks/roles/gh_users/tasks/main.yml
	playbooks/roles/nginx/tasks/main.yml
	playbooks/roles/nginx/templates/basic-auth.j2
	playbooks/roles/nginx/templates/edx_logrotate_nginx_access.j2
	playbooks/roles/notifier/tasks/deploy.yml
	playbooks/roles/notifier/tasks/main.yml
	playbooks/roles/xqueue/defaults/main.yml
	playbooks/roles/xqueue/templates/xqueue_consumer.conf.j2

parameterize machine names in edx-west playbooks -- to edx-west/release

Added a validation on the machine variable, expected to be passed in
from the command line now, so that the worker play only works on
machines named "util" and the app play on machines named "app".
Otherwise it would be too easy to mix those up.

Now that we're using -e command line options, it's easier to use this to
specify the "modify_db" variable than prompt_vars.  Having every install
block on this question before was such a hassle!  Now we just won't
migrate unless you explicitly say so on the ansible command with
"migrate_db=yes" or "migrate_only=yes".

use local temp dir for sockets and ansible cache

I was having problems where concurrent installs could trample on each
other.  The instance that immediately affected me was output caching
from ec2.py: the output of that command is different between staging and
prod, and both were being written to /tmp/ansible_ec2.cache and .index.

Fix here is to write to a local temp directory.  This creates empty temp
dirs to ensure that they are created in all repos.

While less likely, you could have collisions on named ssh sockets.
Those are named with just the instance name, which could be re-used
across VPC's.  Putting those in the ./tmp dir too prevents that.

Note that for consistency I did away with just the plain ec2.ini file,
and instead now there are prod- and stage- variants.  This is clean but
now means that you'll need to change your install command to look
something like this:

    ANSIBLE_EC2_INI=prod-ec2.ini ANSIBLE_CONFIG=prod-ansible.cfg ansible-playbook -c ssh -u ubuntu -i ./ec2.py prod-app.yml

Feanil/release gugelhupf

Update base AMIs.

edx-west: clean up users, remove two unused plays (*-log.yml)

Our user lists were a mishmash, this standardizes them across major
machine types (app servers and workesrs).

On the jumpbox also add Sherif Halaway.  Alejandro was already
provisioned there, adding now as cleanup.

The log machines were abandoned long ago.

Feanil/demo common dep

E0d/dhclient whitespace

Add the common dependency to the demo role.

Feanil/pre release changes

Database related updates to fix dev and full stack vagrant builds.

fixing bigdesk install logic.

Revert "Merge pull request #759 from edx/jarv/change-devstack-to-release...