Repository instances are stored in the 'repository' table. Repositories
in the table are either 'Enabled and visible' or 'Enabled but hidden'.
Hidden repositories still serve their files, but are not visible in the
filepicker UI. Disabling a repository instance removes its record from
the table.
In the original implementation of the plugin manager (see b9934a17), the
method plugintype_repository::get_enabled_repositories() correctly
returned all records from the repository table. Then as a part of the
bigger refactoring in MDL-41437, the commit bde002b8 replaced the
original method with the new get_enabled_plugins() one which started to
return visible repositories only.
As a consequence, the admin tree stopped populating setting page nodes
for hidden repository instances. So attempting to visit their setting
page threw a section error. Credit goes to Ike Quigley for debugging and
tracing this down.
This patch fixes the way how the list of enabled repositories is
populated by the plugin manager so that both visible and hidden
repositories are returned again. This does not affect the filepicker
itself as it is using its own methods for obtaining the list.
Includes:
* update checker refactored to \core\update\ namespace
* plugininfo classes refactored to \core\plugininfo\ namespace
* plugin_manager renamed to core_plugin_manager
* redirect back to original page after plugin uninstall
* fixed assign subplugin uninstall
* move assign subplugins under the assignment in admin tree
* fixed plugininfo for all question related plugin types
* auth uninstall support
* added missing block dependencies
* added theme uninstall
* subplugin types are following the plugin on plugin overview page
* several performance improvements in plugin manager
* new warnigns when plugininfo are outdated or missing
* multiple fixes and other improvements
