^^^^^^^^^^^^^^^^^^
- Refactor template of blog header: now it will display the blog image, if
present, or the blog title, if not. [hvelarde]
- Image field is no longer required by default. [hvelarde]
- In order to fix ordering in plone.abovecontent viewlet manager, we had to
register the plone.path_bar viewlet before everything and then register the
sc.blog.blogheader viewlet after everything. [hvelarde]