Docs: Add revamped activemq TLS keystore instructions

* On its own page, now
* Manual and Puppet examples
* Expanded explanations where needed
Docs WIP: Paste-dump to begin new ActiveMQ config page

This pastes all ActiveMQ knowledge from elsewhere in the docs into a single new
page, which will soon replace all of these scattered XML examples.
Docs: Write new ActiveMQ config guide, based on pasted info
Docs: Edit ActiveMQ config guide based on comments and feedback; add more settings
Docs: Correct bad info about systemUsage in ActiveMQ config guide
Docs: Remove all example activemq.xml config info from other pages

We can now just link to the ActiveMQ config reference.
Examples: Add extensive comments/links to example ActiveMQ configs; add persistence

This commit consists mostly of comments, to help improve the initial ActiveMQ
setup experience.

The one substantive change it makes is adding a persistence adapter to the
multi-broker configs, per something that came up in conversation with RI while
writing these documents.
Docs: Adjustments to activemq config guide

- Fix remaining links
- Harmonize subcollective names with example configs
- Fix typos
- Etc