Since python doesn't have a way to lock deps for a particlar project
by default, I didn't bother with it. This resulted in mkdocs updating at
some point, bringing a breaking change to how tabs are declared and
broken tabs on docs-develop.pleroma.social. I've learned my lesson
and locked deps with pipenv in pleroma/docs!5. This MR updates Pleroma
docs to use the new tab style, fortunately my editor did most of it.
Closes #2045
* It was still written for From Source installs. Now it's both OTP and From Source
* I linked to the cheatsheet where it was about configuration
* I moved the mix tasks of the robot.txt section to the CLI tasks and linked to it
* i checked the code at https://git.pleroma.social/pleroma/pleroma/-/blob/develop/lib/mix/tasks/pleroma/robotstxt.ex and it doesn't seem to more than just this one command with this option
* I also added the location of robot.txt and an example to dissallow everything, but allow the fediverse.network crawlers
* The Thumbnail section still linked to distsn.org which doesn't exist any more. I changed it to a general statemant that it can be used by external applications. (I don't know any that actually use it.)
* Both the logo and TOS need an extra `static` folder. I've seen confusion about that in #pleroma so I added an Important note.
* Added "Migrate" to the title because these steps can also be used to migrate the instance to another server
* Added an optional step to reinstall pleroma (esp. for migrating servers)
* Currently the steps threw an error 'could not execute query: ERROR: function "activity_visibility already exists with the same argument types'
* I added a new step to drop and recreate an empty pleroma-database
* I played around with the `-c` and `-C` options of pg_restore, but dropping and recreating seemd to be the only way I got it working
* This was tested on Debian Stretch, psql (PostgreSQL) 9.6.15
Large part of it was no longer true (i.e none of the changes need
recompilation anymore and you can't brick an instance by changing them,
it's not necessary to manually truncate the db manually anymore)
