add component to display downloading for fasta and csv

frontend/src/views/genes/genes.html

 <div class="genes">
+  <template v-for="(item, index) in downloadAlerts">
+    <v-alert
+      :value="item.value"
+      type="info"
+      icon="fas fa-download"
+      transition="slide-y-transition"
+    >
+      <v-layout align-center>
+        <v-spacer/>
+        {{ item.text }}
+        <v-spacer/>
+        <v-flex md8>
+          <v-progress-linear
+            indeterminate
+            height="2"
+            color="primary"
+          ></v-progress-linear>
+        </v-flex>
+        <v-spacer/>
+    </v-layout>
+    </v-alert>
+  </template>
   <v-layout row wrap>
     <v-flex xs12>
       <v-toolbar

frontend/src/views/genes/genes.js

@@ -162,6 +162,18 @@ export default {
         basename = `${basename}_${this.taxLevel}-${taxName}`;
       }
       return basename;
+    },
+    downloadAlerts() {
+      return [
+        {
+          value: this.loadingFastaDownload,
+          text: "Downloading sequences (.fasta)..."
+        },
+        {
+          value: this.loadingCSVDownload,
+          text: "Downloading metadata (.csv)..."
+        },
+      ]
     }
   },
   mounted() {