Topic themes (#2187)

* Bringing over in-progress changes from topic-core-css

- Adds _espresso-constants.scss;
- Cleanup colors and naming;
- Remove conflict res leftover 'domainObject' in mct-tree.vue;
- Still WIP!

* Various

- Remove pushBack / pullForward functions;
- Fix c-input-inline, remove bg until hover;
- TODO: input bg colors
- Increased margin in main-pane;

* Themeing WIP

- Conductor markup: convert to buttons for accessibility;
- Conductor styles consolidated and changed for better theme support;

* Themeing WIP; significant rewrite of pane headers

- Pane headers restructured for better semantics and clarity;
- Espresso design refined and tightened;
- Grid Vue changes for better themeing support;
- TODO: fix mobile version, collapse icon is whack;

* Restored Number-type input styling for correct positioning of spinner
button;

* Themeing mods for click-icon styles

* Bring Snow theme into style parity with Espresso

- TODO: refine Snow colors;

* Mobile styling fixed

- Mobile menu icon significant fixes;
- Hover only applied to desktop;
- Reorg of mixins;

* Bring Snow theme constants into parity with Espresso

- Refined Snow styles;
- Fixed missing scroll and padding in tree;
- Pane collapse button now uses proper color;
- Item Grid view refinement;
- Cleaned up code;

* Color fixes

- Super-menu description;
- Conductor time buttons hover;
- Datepicker "in-month" items color;
- Espresso colorKeyFilter brightened;

src/plugins/timeConductor/DatePicker.vue

@@ -108,7 +108,7 @@
         grid-gap: 1px;
         height: 100%;
 
-        $mutedOpacity: 0.7;
+        $mutedOpacity: 0.5;
 
         ul {
             display: contents;
@@ -127,7 +127,7 @@
             padding: $interiorMargin;
 
             &.is-in-month {
-                background: rgba($colorBodyFg, 0.1);
+                background: $colorMenuElementHilite;
             }
         }