feat(emails): display current email in interstitial form

src/views/partials/email_update.tpl

@@ -3,7 +3,7 @@
 	<p>[[user:emailUpdate.optional]]</p>
 	<div class="form-group">
 		<label for="email">[[global:email]]</label>
-		<input class="form-control" type="text" id="email" name="email" />
+		<input class="form-control" type="text" id="email" name="email" placeholder="{email}" value="{email}" />
 	</div>
 	<p class="help-block">[[user:emailUpdate.change-instructions]]</p>
 </div>