Faq stuff (rebased onto dev_5_0)



This is the same as gh-1044 but rebased onto dev_5_0.

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Reviewing the FAQs threw up a few items which should be documented - https://trello.com/c/3uqvWhlq/240-faq-issues-needing-moved-to-docs-plone
This is the 1st PR in this effort towards ditching them completely, dealing with troubleshooting issues and ldap.

There is another card for ldap changes - https://trello.com/c/LerTrYZj/118-ldap-docs - which I am happy to also address if someone has time to give me pointers/stick the relevant info in a gdoc or similar.