Add link to index page from repo header, remove page name

Add link to index page from repo header, remove page name

This makes it more obvious how to get back to the index, especially when the
config option `logo-link` is used. And the page name displayed in the header
provided no extra information. It only consumed space and deserved to die.

While at it, make sure that the different parts of the header doesn't wrap
when horizontal space is limited.

Signed-off-by: Lars Hjemli <hjemli@gmail.com>