Plugin Directory: Protect more plugin permalink abuse

[Ipstenu]

I'm opening this to list the companies and larger orgs who have reached out recently regarding being added to the list, as well as some repeat issues that are popping up.

Also adding in 'plugin' -- there are edge cases where it's allowed (plugin management plugins) but it's easier to fix those than to handle the other end.

Putting in a new check for portmanteaus (like 'woopress') and cleaning up some language about trademarks and to please contact us and not resubmit.

[Ipstenu]

strpos

[Ipstenu]

In 11348:

Update the various checkers for restricted terms in plugins

Explain why terms are blocked in a less trademarky fashion

Attempting to block 'woopress' submissions

Fixes #5969