Bug 27740: (follow-up) changed welcome user to <p>

Bug 27740: (follow-up) changed welcome user to <p>

In the 'user_summary block', the "Welcome, user" was an <h3>. This has
been changed to a <p> as it isn't really a heading.

The styling can be changed to make it appear as it was before, or to
make it appear more significant on the page.

To test:
1) Go to the OPAC
2) Go to the home page
3) Go to the 'user_summary' block
4) Check that the part where is says "Welcome, user" is now a <p>

Sponsored-by: Catalyst IT
Signed-off-by: Henry Bolshaw <bolshawh@parliament.uk>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>