Allow to focus select2 elements
Focus select2 elements in modals
Adapt select2 approach used elsewhere

This fixes/improves the focus behavior of the watcher selection
Make attribute expansion focusable
Add attribute expansion styles
Correct icon states when toggling details pane
Merge pull request #1831 from opf/feature/12283_focus_not_set_on_select2_in_modal

12283 focus not set on select2 in modal
Merge pull request #1844 from opf/feature/14436_attribute_expansion_cannot_be_reached_by_keyboard

14436 attribute expansion cannot be reached by keyboard
Merge pull request #1846 from opf/fix/icon-stat-wp-details-buttons