Add historic range query service

To discover the available historic ranges.

src/app/app.module.ts

@@ -56,6 +56,7 @@ import { ChartService } from './services/chart.service';
 import { DataExportService } from './services/data-export.service';
 import { ImageExportService } from './services/image-export.service';
 import { ClimateModelService } from './services/climate-model.service';
+import { HistoricRangeService } from './services/historic-range.service';
 import { IndicatorService } from './services/indicator.service';
 import { ScenarioService } from './services/scenario.service';
 import { ProjectService } from './services/project.service';
@@ -116,6 +117,7 @@ const locationStrategyProvider = {
     DataExportService,
     ImageExportService,
     ClimateModelService,
+    HistoricRangeService,
     IndicatorService,
     ScenarioService,
     ProjectService

src/app/models/historic-range.model.ts

@@ -0,0 +1,4 @@
+export interface HistoricRange {
+    start_year: string;
+    end_year: string;
+}

src/app/services/historic-range.service.ts

@@ -0,0 +1,21 @@
+import { Injectable } from '@angular/core';
+import { Observable } from 'rxjs/Rx';
+
+import { HistoricRange } from '../models/historic-range.model';
+import { ApiHttp } from '../auth/api-http.service';
+import { apiHost } from '../constants';
+
+/*
+ * Historic Range Service
+ * Returns available historic ranges from API
+ */
+@Injectable()
+export class HistoricRangeService {
+
+    constructor(private apiHttp: ApiHttp) {}
+
+    public list(): Observable<HistoricRange[]> {
+        const url = apiHost + '/api/historic-range/';
+        return this.apiHttp.get(url).map(resp => resp.json() || [] as HistoricRange[]);
+    }
+}