Add new solarized light and dark themes.

Add more elements to be controlled by theme css:
- Preloader spinner colours
- Operation disable / breakpoint icons
- Auto bake checkbox
- Search highlight colour
- Categories header colour

src/web/stylesheets/components/_operation.css

@@ -205,19 +205,19 @@ div.toggle-string {
 }
 
 .disable-icon {
-    color: #9e9e9e;
+    color: var(--disable-icon-colour);
 }
 
 .disable-icon-selected {
-    color: #f44336;
+    color: var(--disable-icon-selected-colour);
 }
 
 .breakpoint {
-    color: #9e9e9e;
+    color: var(--breakpoint-icon-colour);
 }
 
 .breakpoint-selected {
-    color: #f44336;
+    color: var(--breakpoint-icon-selected-colour);
 }
 
 .break {