docs migration: Container Lifecycle Hooks into Concepts (#2564)

* initial commit for structure

* migrate Container Lifecycle Hooks and related files to Concepts

* update Concepts ToC

* fix formatting

* Formatting tweaks

* comment out What's next

* remove What's next

* Begin rewrite of container-lifecycle-hooks.md

* incremental update to edit

* Split Container Lifecycle Hooks into container-lifecycle-hooks.md and container-environment.md; change all referring links.

* Add concept template to volumes.md and images.md

* Apply changes for steveperry-53 feedback.

* fix format issue

* tweak formatting

* fix Concepts ToC

* update links

* add back changes to Concepts ToC

* fix a link

* update links

docs/admin/index.md

@@ -4,4 +4,4 @@ title: Admin Guide
 
 {% include user-guide-content-moved.md %}
 
-[Cluster Administration Overview](/docs/tasks/administer-cluster/overview/)
+[Cluster Administration Overview](/docs/tasks/administer-cluster/overview/)