Add zindex to panel (#736)

* Add z-index options back to panel

* Add formatting for z-index panel buttons

* make z-index buttons all the same width

* make z-index button spacing even

* use svg icons & translations

* add ui legend

Co-authored-by: David Luzar <luzar.david@gmail.com>

src/styles.scss

@@ -87,6 +87,7 @@ button,
   border-radius: 4px;
   margin: 0.125rem 0;
   padding: 0.25rem;
+  white-space: nowrap;
 
   cursor: pointer;
 
@@ -248,6 +249,11 @@ button,
   white-space: nowrap; /* added line */
 }
 
+.zIndexButton {
+  width: 26px;
+  margin: 0 5px;
+}
+
 .scroll-back-to-content {
   position: fixed;
   left: 50%;