table panel: additional fixes for value to text mapping

Make the value to text mapping more similar to singlestat solution.
Adds more tests.
Also, allows string to be mapped to other string besides numeric values.

public/app/plugins/panel/table/column_options.ts

@@ -113,29 +113,30 @@ export class ColumnOptionsCtrl {
       this.render();
     };
   }
-  addValueMapping(style) {
-    if (!style.valueMappings) {
-      style.valueMappings = [];
+
+  addValueMap(style) {
+    if (!style.valueMaps) {
+      style.valueMaps = [];
     }
-    style.valueMappings.push({ value: '', text: '' });
+    style.valueMaps.push({ value: '', text: '' });
     this.panelCtrl.render();
   }
 
-  removeValueMapping(style, index) {
-    style.valueMappings.splice(index, 1);
+  removeValueMap(style, index) {
+    style.valueMaps.splice(index, 1);
     this.panelCtrl.render();
   }
 
-  removeRangeMapping(style, index) {
-    style.rangeMappings.splice(index, 1);
-    this.panelCtrl.render();
-  }
-
-  addRangeMapping(style) {
-    if (!style.rangeMappings) {
-      style.rangeMappings = [];
+  addRangeMap(style) {
+    if (!style.rangeMaps) {
+      style.rangeMaps = [];
     }
-    style.rangeMappings.push({ from: '', to: '', text: '' });
+    style.rangeMaps.push({ from: '', to: '', text: '' });
+    this.panelCtrl.render();
+  }
+
+  removeRangeMap(style, index) {
+    style.rangeMaps.splice(index, 1);
     this.panelCtrl.render();
   }
 }