We may want to switch or extend it to display name. I leave it like this for now, continued work on this needs to have sortable columns in mind

Fire up server request only on typing printed or modifying characters and when the string actually changed

When emptying a list, a hidden entry remains. If the user uid is the same as of a user being to be loaded, it will not be appended but removed. Thus, add a random user name to avoid such happenings.

move group-click initialization to groups.js and only react on elements with a data-gid attribute given

set admin gid to Admins filter. I.e. hard-coding the admin group, but this is OC reality atm - other admin groups are not possible.