Misc UI 6 (#2338)

* Sanding and shimming on loading CSS

- Wait spinners in the tree;
- Move spinner and loading CSS from legacy to global.scss;

* Misc UI 6
- Better approach to Time Conductor overflow;
- Fixed main page left/right clipping issue;
- Fixed table header bg styling that had issues in legacy tables;
- Fixed Time Conductor datetime picker clipping issue;
- New .c-message--simple for use in Summary Widgets;
- Better styling for header in empty Tabs view;
- Fixed Chrome 73 scrolling bug in Summary Widgets;
- Fixed problem in Inspector <li> elements from new wait spinner;
- Fixed color of <a> tags in tables to be more visible;
styling;

* Misc UI 6

- Fix VISTA session selector not scrolling (Chrome 73 overflow bug);

* Misc UI 6

- Fix VISTA session selector not scrolling (Chrome 73 overflow bug);

src/plugins/timeConductor/Conductor.vue

@@ -126,7 +126,6 @@
             grid-template-rows: 1fr;
             grid-template-columns: 20px auto 1fr auto;
             grid-template-areas: "tc-mode-icon tc-start tc-ticks tc-end";
-            overflow: hidden;
         }
 
         &__mode-icon {