Add vue component for confirmation popover

Have the confirmation popover in a separate Vue component fixes a bug in
IE that was causing the `form` element in the popover to be ignored.

Since `form`s cannot be nested, the `form` element in the popover was
being discarded by IE and the revoke/resend invitation buttons did
nothing.

Breaking the functionality into a Vue component moves the `form` into a
separate template. When the popover is displayed, the component is added
to the DOM at the end, so the `form` is properly not-nested.

templates/components/confirmation_button.html

@@ -1,19 +1,10 @@
-{% macro ConfirmationButton(btn_text, action, csrf_token, confirm_msg="Are you sure?", confirm_btn="Confirm", cancel_btn="Cancel") -%}
-  <v-popover placement='top-start'>
-    <template slot="popover">
-      <p>{{ confirm_msg }}</p>
-      <div class='action-group'>
-        <form method="POST" action="{{ action }}">
-          {{ csrf_token }}
-          <button class='usa-button usa-button-primary' type='submit'>
-            {{ confirm_btn }}
-          </button>
-        </form>
-        <button class='usa-button usa-button-secondary' v-close-popover>
-          {{ cancel_btn }}
-        </button>
-      </div>
-    </template>
-    <button class="tooltip-target" type="button">{{ btn_text }}</button>
-  </v-popover>
+{% macro ConfirmationButton(btn_text, action, confirm_msg="Are you sure?", confirm_btn="Confirm", cancel_btn="Cancel") -%}
+  <confirmation-popover
+    btn_text='{{ btn_text }}'
+    action='{{ action }}'
+    csrf_token='{{ csrf_token() }}'
+    confirm_msg='{{ confirm_msg }}'
+    confirm_btn_text='{{ confirm_btn }}'
+    cancel_btn_text='{{ cancel_btn }}'>
+  </confirmation-popover>
 {%- endmacro %}