Add a bootstrap element.

Change-Id: Ic300e39a56f401be4d88feb6cdf85c851982282c
Add a horizon element.

Change-Id: Ie585a7ea63ba5b5b8b064df738e9616827e913fa
TO PROPOSE: Touch a first-boot.status file:

After running first-boots scripts, both to indicate
that the scripts have completed, and also to record
the exit status.

This is useful for automated testing:
  - tests can wait until first-boot scripts have
    completed before commencing testing
  - tests can abort further testing if first-boot
    scripts have failed.

Change-Id: Idec63de858c15def8c621056232aad45eab225e8
DO NOT MERGE: tim element

Change-Id: I2d8927a391306b21cac0a913153dbd3fc3c4ace4
DO NOT MERGE: bin/boot-elements

Change-Id: I0d4e61d0f00a8635ad27c37eb96d226269f27ab3
remove use-config-templates from cinder-config:

use-config-templates has been deprecated, and must
not be used by the cinder element.

This change relies on os-refresh-config instead.

Change-Id: Ie8594fa99d05032fa0e7a425a9dd278910b80cab