This way we make it easier to modify.
Note that, since the title of the page is "Administration" and it's in
the "Admin" section, we're adding an option to the `header` method in
order to avoid having a confusing title like "Administration - Admin".
Also note that, by removing the `title` HTML class, we avoid inheriting
styles from the `dashboard.scss` stylesheet, and now the heading is
displayed in the position it was meant to.
Finally, the concept of using a `main-class` for the current page comes
from a branch (currently in development) which will replace the <div>
tag with the `admin-content` class with a `main` tag.
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