* Show splitview icons in the sidebar popup menu to reinforce the connection
and disambiguate the terms "horizontal" & "vertical"
* Don't programmatically compute spritesheet offset in SidebarView.js, and
avoid using `background-position-y` (which apparently is not W3C and isn't
supported in Firefox)

Plus two small cleanups I hit upon while working on this:

* Remove unneeded appReady() code in WorkingSetView (also fwiw, it should
have been htmlReady() anyway)
* Fix out of date comments in DefaultMenus
- Tweak splitview icon vertical alignment per @larz0
- Fix JSHint nit: unused local var
Initial commit.
Tweaked pane-header lines.
Updated by ALF automation.
Merge pull request #9165 from adobe/alf_localization

ALF Automation
Updated by ALF automation.
Merge pull request #9177 from adobe/alf_localization

ALF Automation
fix editor redrawing test failures
Merge pull request #9154 from adobe/pflynn/splitview-menu-icons

Show splitview icons in the sidebar popup menu
Merge pull request #9178 from adobe/jeff/fix-editor-tests

Fix editor redrawing test failures
Merge pull request #9164 from adobe/larz/issue-9146

Made the split separator darker
Merge remote-tracking branch 'upstream/master'