Conditionals and Notebook UI fixes (#2868)

- Significant fixes for Safari-compatible Flex layout in Condition Set
view;
- Changed visual approach to current-value section;
- Firefox scrollbar coloring
- Fix layout issues in Firefox;
- Consolidate Conditionals styles into single scss file;
- Fix test datum elements layout, better wrapping;
- Better approach to presence/absence of URL property in Condition
Widget;
- Fixes #2853;
- Fix errors in URL property handling in Condition Widget;
- Fixes #2853;
- Fixes #2867 - hide the View Switcher when an object is being edited;
- Refined titling on View Switcher and Notebook menu button;
- Cleaned up styles in l-browse-bar and moved into
ui/layout/layout.scss;
- Removed styles/_layout.scss;
- Hide the main view Edit button when in mobile

src/plugins/notebook/components/notebook-menu-switcher.vue

@@ -1,8 +1,8 @@
 <template>
-<div class="l-browse-bar__view-switcher c-ctrl-wrapper c-ctrl-wrapper--menus-left">
+<div class="c-menu-button c-ctrl-wrapper c-ctrl-wrapper--menus-left">
     <button
         class="c-button--menu icon-notebook"
-        title="Switch view type"
+        title="Take a Notebook Snapshot"
         @click="setNotebookTypes"
         @click.stop="toggleMenu"
     >