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".

Conflicts:
	playbooks/edx-west/carnegie-prod-app.yml
	playbooks/edx-west/carnegie-prod-worker.yml
	playbooks/edx-west/cme-prod-app.yml
	playbooks/edx-west/cme-prod-worker.yml
	playbooks/edx-west/stage-app.yml

Conflicts:
	playbooks/edx-west/prod-app.yml
	playbooks/edx-west/prod-worker.yml
	playbooks/edx-west/stage-app.yml
	playbooks/edx-west/stage-worker.yml

Spell things correctly.

Feanil/always update cache prefixes

Break after tagging.

Sleep between adding aws tags.

extra value to format.

Jarv/add pkgs to jenkins

create alias for bastion

also some formatting fixes in the output, renaming jumpbox to bastion

adding doc-opts, needed for the ssh config script

Added HTTP Strict Transport Security headers to ensure clients always

changing secure var location

Jarv/key optional

useful for when relying on ssh-agent

Remove vagrant version requirement

Updates to play and a fix to the role.

Feanil/tag amis