NEW KEP: Update 'contact' object

[Thomas Brüderli]

Alain Abbas wrote:
> Could be mor simple to put preferred="1" in the <email /> entry instead
> to make a duplicate entry <preferred> that is always hard to maintains.
> Example
> <email displayname="aa" preferred="1>aa at aa.com</email>
> <email displayname="bb"> bb at bb.com</email>

Also in this case inconsistency can arise:

<email displayname="aa" preferred="1">aa at aa.com</email>
<email displayname="bb" preferred="1">bb at bb.com</email>

> like that e are sure to not have duplicate infos and false info
> in case of :
> <email displayname="bb"> bb at bb.com</email>
> <preferred>
> <email>toto at toto.com</email>
> </preferred>

In either case, the client altering a contact object is responsible to 
ensure consistent data whereas the latter case is IMO preferable because 
it doesn't require iteration over all <email> nodes for both reading the 
preferred email address and setting/changing it.

~Thomas