Redmine#4848: fix peers, peerleader, and peerleaders documentation
Additional links and markup for sys overview docs.
Merge branch 'system-overview' of https://github.com/KevWright/documentation into system-overview-ii
Fixed some meta data in system overview files
Document new filter attributes.

Mark old filter attributes as deprecated, they are no longer functional.
Merge pull request #378 from KevWright/system-overview-ii

System overview updates
Clarify how include and exclude statements are combined.
Document new admit/deny attributes and resource identification.

Rewrite/organize introduction to access promises. Enterprise specific
functionality needs more information.
Merge pull request #379 from vohi/document_filter_attributes

Document new filter attributes.
Incorporate comments from review
Merge pull request #381 from vohi/document_admit_deny_attributes

Document new admit/deny attributes and resource identification.
Documentation for protocol-version management attributes.
Document allowciphers.
Better English, comment from review
Fix header
Move overviews out of getting started.

This should be what is wanted, and fixes Jekyll complaining.
Fix manuals, leave top-level until subpages are re-categorized
reference/promise-types/access.markdown: fix examples and add snippets
Fixed Categories in Overviews
Merge pull request #382 from KevWright/fix-categories

Fixed Categories in Overviews