add limit by

pdb-js/src/app/limit-by/limit-by.component.html

@@ -0,0 +1,22 @@
+<mat-form-field id="limitBy">
+  <mat-label>Limit By:</mat-label>
+  <mat-select [(value)]="limitBy">
+    <mat-option value="NO_LIMIT">no limit</mat-option>
+    <mat-option value="MOST_VALUES">most values</mat-option>
+    <mat-option value="FEWEST_VALUES">fewest values</mat-option>
+    <mat-option value="MAX_VALUE">max value</mat-option>
+    <mat-option value="MIN_VALUE">min value</mat-option>
+  </mat-select>
+</mat-form-field>
+
+<mat-form-field id="limit"
+  *ngIf="limitBy !== 'NO_LIMIT'">
+  <input 
+    matInput 
+    type="number" 
+    placeholder="Limit" 
+    min="1" 
+    value="{{limit}}"
+    
+    >
+</mat-form-field>