Add explanations for deactivate user and block user buttons in admin

Author: nlalonde

app/assets/javascripts/admin/templates/user.js.handlebars

@@ -85,6 +85,7 @@
       {{#if active}}
         {{#if can_deactivate}}
           <button class='btn' {{action deactivate target="content"}}>{{i18n admin.user.deactivate_account}}</button>
+          {{i18n admin.user.deactivate_explanation}}
         {{/if}}
       {{else}}
         {{#if can_send_activation_email}}
@@ -163,6 +164,7 @@
         </button>
       {{/if}}
     {{/if}}
+    {{i18n admin.user.banned_explanation}}
     </div>
   </div>
   <div class='display-row'>

config/locales/client.en.yml

@@ -1172,6 +1172,8 @@ en:
         deactivate_failed: "There was a problem deactivating the user."
         unblock_failed: 'There was a problem unblocking the user.'
         block_failed: 'There was a problem blocking the user.'
+        deactivate_explanation: "A deactivated user must validate their email again before logging in."
+        banned_explanation: "A banned user can't log in."
         block_explanation: "A blocked user can't post or start topics."