Working on the docs.elgg.org migration (part 2)

this is a work in progress for #6812 

keep in mind the following comment: https://community.elgg.org/discussion/view/1922226/documentation-work

> Also I'd remind reviewers that we shouldn't nitpick at quality when porting docs over from the wiki. Let's just get them transferred and get docs.elgg.org turned down. Then we can review the state of affairs and see what's most needed wrt reorg or quality improvements. That presents docs translators with a small amount of churn but I think based on our development pace it won't actually be that bad (and there aren't many docs translators anyways).

this PR contains the following old docs.elgg.org pages

- [Engine/PageOwnership](http://docs.elgg.org/wiki/Engine/PageOwnership)
- [Engine/Views/SimpleCache](http://docs.elgg.org/wiki/Engine/Views/SimpleCache)
- [What should I use to edit php code?](http://docs.elgg.org/wiki/What_should_I_use_to_edit_php_code%3F)
- [Backup and Restore](http://docs.elgg.org/wiki/Backup_and_Restore)
- [FTPBackupScript](http://docs.elgg.org/wiki/FTPBackupScript)
- [Gatekeeper](http://docs.elgg.org/wiki/Gatekeeper)
- [Changing profile fields](http://docs.elgg.org/wiki/Changing_profile_fields)
- [Changing registration](http://docs.elgg.org/wiki/Changing_registration)
- [Plugin Guidelines](http://docs.elgg.org/wiki/Plugin_Guidelines)
- [I don't like the wording of something in Elgg. How do I change it?](http://docs.elgg.org/wiki/I_don%27t_like_the_wording_of_something_in_Elgg._How_do_I_change_it%3F)
- [Move site](http://docs.elgg.org/wiki/Move_site)
- [How do I find the code that does x?](http://docs.elgg.org/wiki/How_do_I_find_the_code_that_does_x%3F)
- [Engine/Controllers/BestPractices](http://docs.elgg.org/wiki/Engine/Controllers/BestPractices)
- [Getting Help](http://docs.elgg.org/wiki/Getting_Help)
- [How does registration work?](http://docs.elgg.org/wiki/How_does_registration_work%3F)
- [Javascript/Ajax](http://docs.elgg.org/wiki/Javascript/Ajax)
- [Dont Modify Core](http://docs.elgg.org/wiki/Dont_Modify_Core)
- [How do I change PHP settings using .htaccess?](http://docs.elgg.org/wiki/How_do_I_change_PHP_settings_using_.htaccess%3F)
- [HMAC Authentication](http://docs.elgg.org/wiki/HMAC_Authentication)
- [Manually add user](http://docs.elgg.org/wiki/Manually_add_user)
- [Diagnostics](http://docs.elgg.org/wiki/Diagnostics)
- [Debug mode](http://docs.elgg.org/wiki/Debug_mode)
- [Plugin order](http://docs.elgg.org/wiki/Plugin_order)
- [Finding plugins](http://docs.elgg.org/wiki/Finding_plugins)
- [Https login turned on accidently](http://docs.elgg.org/wiki/Https_login_turned_on_accidently)
- [Using a test site](http://docs.elgg.org/wiki/Using_a_test_site)
- [What events are triggered on every page load?](http://docs.elgg.org/wiki/What_events_are_triggered_on_every_page_load%3F)
- [500 - Internal Server Error](http://docs.elgg.org/wiki/500_-_Internal_Server_Error)
- [PluginDependencies](http://docs.elgg.org/wiki/PluginDependencies)
- [Javascript/hooks](http://docs.elgg.org/wiki/Javascript/hooks)
- [Security FAQ](http://docs.elgg.org/wiki/Security_FAQ)
- [How to restrict where widgets can be used](http://docs.elgg.org/wiki/How_to_restrict_where_widgets_can_be_used)
- [When I upload a photo or change my profile picture I get a white screen](http://docs.elgg.org/wiki/When_I_upload_a_photo_or_change_my_profile_picture_I_get_a_white_screen)
- [Filtering](http://docs.elgg.org/wiki/Filtering)
- [CSS is missing](http://docs.elgg.org/wiki/CSS_is_missing)
- [Should I edit the database manually?](http://docs.elgg.org/wiki/Should_I_edit_the_database_manually%3F)
- [Page not found](http://docs.elgg.org/wiki/Page_not_found)
- [IE login problem](http://docs.elgg.org/wiki/IE_login_problem)
- [System diagnostics](http://docs.elgg.org/wiki/System_diagnostics)
- [Emails don't support non-Latin characters](http://docs.elgg.org/wiki/Emails_don%27t_support_non-Latin_characters)
- [Session length](http://docs.elgg.org/wiki/Session_length)
- [Copy a plugin](http://docs.elgg.org/wiki/Copy_a_plugin)
- [File is missing an owner](http://docs.elgg.org/wiki/File_is_missing_an_owner)
- [No images](http://docs.elgg.org/wiki/No_images)
- [SystemLog](http://docs.elgg.org/wiki/SystemLog)
- [Deprecation warnings](http://docs.elgg.org/wiki/Deprecation_warnings)
- [Javascript not working](http://docs.elgg.org/wiki/Javascript_not_working)
- [Loggable](http://docs.elgg.org/wiki/Loggable)
- [Accessibility Guidelines](http://docs.elgg.org/wiki/Accessibility_Guidelines)
- [Walled Garden](http://docs.elgg.org/wiki/Walled_Garden)