put y axis definition into its own object

pdb-js/src/app/plot.service.ts

@@ -193,13 +193,11 @@ export class PlotRequest {
   thumbnailMaxHeight : number = 200;
   groupBy : Array<string>;
   limitBy : string;
-  axisScale : string;
   limit : number;
+  y1:YAxisDefinition;
+  y2:YAxisDefinition;
   dateRange : string;
   aggregates : Array<string>;
-  yRangeMin : number;
-  yRangeMax : number;
-  yRangeUnit  : string;
   keyOutside : boolean = false;
   generateThumbnail : boolean;
   
@@ -208,6 +206,13 @@ export class PlotRequest {
   }
 }
 
+export class YAxisDefinition {
+  axisScale : string;
+  yRangeMin : number;
+  yRangeMax : number;
+  yRangeUnit  : string;
+}
+
 export class PlotResponse {
   imageUrl : string;
   stats : PlotResponseStats;