* Improve feed item pane header (fixes#4141)
* Show item pane custom head when headerMode is none (fixes#4116)
* fx115: Fix button style on windows (fixes#4120)
* Move split-menu-button styles to SCSS
This reverts commit ecea550a37.
It seems to be causing various UI issues, including the items list
sliding under the item pane when the collections pane is expanded
(though I can no longer reproduce that).
