Docs - various documentation related chores/cleanups

[dauer]

Fix Markdown links syntax, should be Asciidoctor

Shiro Plugin has a new maintainer - changed link

Fixed typo: (l)GrailsConcurrentMapCacheManager

Minor code example clean up

Consistent descriptions - only Geb2 had ending '.'

[jdaugherty]

So it seems that the "ddos" mentioned on https://status.apache.org caused the block of several github related ips.

https://infra.apache.org/abc/#bots shows 64.236.131.241 was blocked. We need to discuss with infrastructure - if they're blocking the github runners, we may be better off running our own self-hosted runners @jamesfredley @matrei

[jdaugherty]

So it seems that the "ddos" mentioned on https://status.apache.org caused the block of several github related ips.

https://infra.apache.org/abc/#bots shows 64.236.131.241 was blocked. We need to discuss with infrastructure - if they're blocking the github runners, we may be better off running our own self-hosted runners @jamesfredley @matrei

I posted about this in slack on the infrastructure channel asking for guidance.