fix(datepicker): reseting min and max boundaries will reset it in datepicker (#3112)

fixes #3085

Author: valorkin

src/datepicker/bs-datepicker.component.ts

@@ -207,8 +207,8 @@ export class BsDatepickerComponent implements OnInit, OnDestroy, OnChanges {
     this._config = Object.assign({}, this._config, this.bsConfig, {
       value: this._bsValue,
       isDisabled: this.isDisabled,
-      minDate: this.minDate || this._config.minDate,
-      maxDate: this.maxDate || this._config.maxDate
+      minDate: this.minDate || this.bsConfig && this.bsConfig.minDate,
+      maxDate: this.maxDate || this.bsConfig && this.bsConfig.maxDate
     });
   }
 

src/datepicker/bs-daterangepicker.component.ts

@@ -188,8 +188,8 @@ export class BsDaterangepickerComponent
       {
         value: this._bsValue,
         isDisabled: this.isDisabled,
-        minDate: this.minDate || this._config.minDate,
-        maxDate: this.maxDate || this._config.maxDate
+        minDate: this.minDate || this.bsConfig && this.bsConfig.minDate,
+        maxDate: this.maxDate || this.bsConfig && this.bsConfig.maxDate
       }
     );
   }