Split into distinct docker images with version tags

[gberche-orange]

Thanks @ArthurHlt for sharing the concourse-container docker images.

Currently, the containers (terraform, uaa, bosh, ...) are exposed as a single image in docker hub with tag allowing selection among the latest build of each type.

Since different concourse installations might need to upgrade the different containers at different times, it would be useful to have distinct docker images and associated version tag (at least for the leaf images such as terraform).

Relates to orange-cloudfoundry/cf-ops-automation#1 (comment)

/CC @o-orand