use one multi-select drop down for plot type

All plot types we currently have can be combined
in one image. So there is no need to compute
combinable types.

pdb-js/src/app/visualization-page/visualization-page.component.ts

@@ -23,12 +23,9 @@ export class VisualizationPageComponent implements OnInit {
   
   availablePlotTypes = {};
   
-  selectedPlotType = new FormControl('');
+  selectedPlotType = [];
   plotTypes: Array<any>;
-  
-  selectedCombinePlotType = new FormControl('');
-  combinePlotTypes: Array<any>;
-  
+    
   tagFields: Array<TagField> = new Array<TagField>();
   
   groupBy = new Array<TagField>();
@@ -66,12 +63,10 @@ export class VisualizationPageComponent implements OnInit {
   ngOnInit() {
     const that = this;
     this.plotTypes = this.plotService.getPlotTypes();
-    this.selectedPlotType.setValue(this.plotTypes[0]);
+    this.selectedPlotType.push(this.plotTypes[0]);
     
     this.plotTypes.forEach(pt => this.availablePlotTypes[pt.name] = pt);
-    
-    this.combinePlotTypes = this.getCombinablePlotTypes(this.selectedPlotType.value);
-    
+        
     that.plotService.getFilterDefaults().subscribe(function(filterDefaults) {
     
       filterDefaults.fields.forEach(function(name) {
@@ -85,16 +80,6 @@ export class VisualizationPageComponent implements OnInit {
       that.splitBy = that.tagFields.find(val => filterDefaults.splitBy == val.name);
     });
     this.yAxisScale = "LOG10";
-    
-    this.selectedPlotType.valueChanges.subscribe(function(selectedMainPlotType){
-      that.combinePlotTypes = that.getCombinablePlotTypes(selectedMainPlotType);
-      if (!that.combinePlotTypes.includes(that.selectedCombinePlotType.value)){
-        that.selectedCombinePlotType.setValue('');
-      }
-    },
-    error => {
-      that.showError(error.error.message);
-    });
   }
     
   getCombinablePlotTypes(selectedMainPlotType) : Array<any>{
@@ -137,10 +122,7 @@ export class VisualizationPageComponent implements OnInit {
   
   createPlotRequest(): PlotRequest {
     const aggregates = [];
-    aggregates.push(this.selectedPlotType.value.id);
-    if (this.selectedCombinePlotType.value){
-      aggregates.push(this.selectedCombinePlotType.value.id);
-    }
+    this.selectedPlotType.forEach(a => aggregates.push(a.id));
     
     const request = new PlotRequest();
     request.query = this.query.query;