contacts: rename "name" to "first_name", and add explit getters.

contacts: rename "name" to "first_name", and add explit getters.

we've created it with just "name", then we split in a very hackish
way. Make it more sane now:
 - first name: comes from DB
 - last name: comes from DB
 - full name: created on the fly, when needed. cached.

all the getters return references to internal stringshares.