*add + sign to 'Add new class' button

*fix linting and rest snapshot
*fix ts-lint issue: Compiler option 'extends' requires a value of type string according to: palantir/tslint#3643

src/app/components/spinner/spinner.component.ts

@@ -21,7 +21,7 @@ IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
 CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */
 
-import { Component, OnDestroy, OnInit, Input } from '@angular/core';
+import { Component, OnDestroy, OnInit } from '@angular/core';
 import { merge, Observable, Subscription, timer } from 'rxjs';
 import { debounce, distinctUntilChanged, partition, switchMap } from 'rxjs/operators';
 import { PendingInterceptorService } from '../../services/spinner/pending-interceptor.service';