[Shtoom] Address book support added

[Casper Wilstrup]

Hi shtoom'ers

I've just checked address book support into svn. Check it out from the
gnome GUI. Support in the other Linux GUI's is on the way.

The design is interface based, so it should be easy to develop extra
address books. Just add a file implementing the AddressBook interface.

To edit your address book, click on the '...' button next to the address
entry in the gnome GUI. Click the '+' button, and add entries.

To dial an entry in your address book, just type 'addr:friend' and click
'Call', the nickname 'friend' is automatically looked up in the address
book, and the address is substituted by the sip address of 'friend'. The
prefix 'addr:' can be ommitted. It just indicates that the address is
from the default address books. Future address book implementations
should select their own prefix, like 'ldap:', 'evo:' and the like.

I will do the following, before leaving the address book project:

1. Implement the address book GUI in 'wxwindows', 'qt', and 'tkinter'
2. Write an evolution address book.

Volunteers who would like to add support in the windows and mac GUI's
are more than welcome. Also developing address books for your favorite
application would be cool.

And obviously, bug reports are more than welcome too.

/Casper