confirmation modal for deleting an application

- adds delete-confirmation Vue component
- refactors some button styles to make them globally available

styles/components/_portfolio_layout.scss

@@ -213,12 +213,6 @@
           border-top: 0;
           padding: 3 * $gap 2 * $gap;
 
-          .usa-button-secondary {
-            color: $color-red;
-            background-color: $color-red-lightest;
-            box-shadow: inset 0 0 0 1px $color-red;
-          }
-
           .usa-button-disabled {
             color: $color-gray-medium;
             background-color: $color-gray-lightest;
@@ -271,10 +265,6 @@
       height: 4rem;
     }
 
-    .usa-button-danger {
-      background: $color-red;
-    }
-
     select {
       padding-left: 1.2rem
     }