add Requests and Contacts interfaces

Objects implementing org.freedesktop.Telepathy.Connection interface must also implement:
* org.freedesktop.Telepathy.Connection.Interface.Requests
* org.freedesktop.Telepathy.Connection.Interface.Contacts

Signed-off-by: Maksim Melnikau <maxposedon@gmail.com>
start Connection.Interface.ContactList implementation

Signed-off-by: Maksim Melnikau <maxposedon@gmail.com>
add "empty" contacts response && fix typo

Signed-off-by: Maksim Melnikau <maxposedon@gmail.com>
basic GetContactListAttributes implementation

Signed-off-by: Maksim Melnikau <maxposedon@gmail.com>