messages.xml: Personalize the LDAP login strings

Users have no idea what LDAP is, so let's try to make this a little
easier for them.
xmlui: verdana -> Verdana

Fix font names in all styles
xmlui: Fix font-family hierarchy

In case the user doesn't have Verdana installed, try for some other
sans-serif fonts, and then fall back on any "sans-serif" if need be.
xmlui: Clean up superfluous font declarations

Unneeded font-family declarations in base.css and style.css:

find modules/xmlui/src/ -iname "base.css" -exec sed -i "/font-family:/d" {} \;
find modules/xmlui/src/ -iname "style.css" -exec sed -i '16,${/font-family/d}' {} \;

This makes the fonts more standard and predictable, and also saves
parsing time.