fix(datepicker): add missing show header input (#1889)

Author: yggg

src/framework/theme/components/datepicker/datepicker.component.ts

@@ -116,6 +116,12 @@ export abstract class NbBasePicker<D, T, P>
    */
   @Input() hideOnSelect: boolean = true;
 
+  /**
+   * Determines should we show calendars header or not.
+   * @type {boolean}
+   */
+  @Input() showHeader: boolean = true;
+
   /**
    * Calendar component class that has to be instantiated inside overlay.
    * */
@@ -348,6 +354,7 @@ export abstract class NbBasePicker<D, T, P>
     this.picker.monthCellComponent = this.monthCellComponent;
     this.picker._yearCellComponent = this.yearCellComponent;
     this.picker.size = this.size;
+    this.picker.showHeader = this.showHeader;
     this.picker.visibleDate = this.visibleDate;
   }