minor #438 Tweaked the admin form views (javiereguiluz)

This PR was squashed before being merged into the master branch (closes #438).

Discussion
----------

Tweaked the admin form views

* Removed the author email from the form (you can only create posts for yourself)
* Added some help messages for form fields (they are not displayed to the end-user yet)
* Tweaks to the design of the error messages:

| Before | After
| --- | ---
| ![before-error](https://cloud.githubusercontent.com/assets/73419/22024956/2056efd0-dccc-11e6-93fd-4bcd5c2b401a.png) | ![after-error](https://cloud.githubusercontent.com/assets/73419/22024959/20f2fa24-dccc-11e6-846b-c5338cba3511.png)

Commits
-------

4aadb5a Tweaked the admin form views

Author: javiereguiluz

app/Resources/views/admin/blog/new.html.twig

@@ -12,9 +12,7 @@
         {{ form_row(form.publishedAt) }}
 
         <input type="submit" value="{{ 'label.create_post'|trans }}" class="btn btn-primary" />
-
         {{ form_widget(form.saveAndCreateNew, { label: 'label.save_and_create_new', attr: { class: 'btn btn-primary' } }) }}
-
         <a href="{{ path('admin_post_index') }}" class="btn btn-link">
             {{ 'action.back_to_list'|trans }}
         </a>

web/css/main.css

@@ -147,9 +147,13 @@ footer #footer-resources i {
     padding: 1em
 }
 
-.form-group.has-error .help-block ul {
+.form-group.has-error .help-block ul,
+.form-group.has-error .help-block li {
     margin-bottom: 0
 }
+.form-group.has-error .help-block li + li {
+    margin-top: 0.5em;
+}
 
 textarea {
     max-width: 100%