add select2 to app specific thirdparty
replace chosen with select2 to provide ajaxified user and group selection for files_external, fixes #7499

remove minified select2 js

show avatars for users, simpler results

remove unneeded users and groups from settings template

fix css, escape user and group names
fix deletion of shares
no need to load user display names
add lookup route for displaynames
use displayname lookup route in files_external settings
Use AppFramework instead of custom controller
Merge pull request #8507 from owncloud/ajaxify_user_list_for_files_external

Ajaxify user list for files external