Removed html formating from address book backend classes. Added

Removed html formating from address book backend classes. Added
fullname() method to addressbook_backend class. Moved
htmlspecialchars() sanitizing from address book backend classes to
html output code. If third party code displays errors from address
book object in html, errors must be sanitized and ASCII line feeds
should be converted to html line breaks.

'addressbook' strings are replaced with 'address book'. Spellcheck
fails on 'addressbook'.

git-svn-id: https://svn.code.sf.net/p/squirrelmail/code/trunk/squirrelmail@11181 7612ce4b-ef26-0410-bec9-ea0150e637f0