initial version of the query autocompletion

Missing features at this point:
1. No suggestions when the input gets the focus.
2. Suggestions are not shown after selecting a suggestion.

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

@@ -1,6 +1,5 @@
 import { Component, OnInit } from '@angular/core';
 import { PlotService, PlotType } from '../plot.service';
-import { HttpClient } from '@angular/common/http';
 import { Observable } from 'rxjs/Observable';
 import { FormControl } from '@angular/forms';
 
@@ -30,7 +29,7 @@ export class VisualizationPageComponent implements OnInit {
   
   query: string;
 
-  constructor(private plotService: PlotService, private http: HttpClient) {
+  constructor(private plotService: PlotService) {
   }
 
   ngOnInit() {