Add "Last updated" timestamps to all documents

[f-trivino]

IPA designs and all documents on https://www.freeipa.org/ should have a "created" field and "updated" field for major updates to a document. Right now it's impossible to say if a design or howto is recent or outdated information from 10 years ago. Bonus points if the design includes a list of IPA versions.

[antoniotorresm]

This information should be available in the database dumps, so this issue is a matter of parsing the DB and adding the info to current docs.