Commit 813eafc0 changed how formatted
name (FN) properties from vCards are imported, so that now an import
involving de-duplication can result in a single contact with multiple
nicknames (setNickname() actually adds nicknames if the new nickname
does not match a previously set nickname).

The contact cache provided by libcontacts is intended for use by
privileged applications only.  Its functionality does not make sense
for non-privileged clients, and cannot be tested correctly when
run in non-privileged mode.

change suggested in review by mvogt

UIDs found in VCF are not very reliable; if a UID match is found where
the contacts have name details that do not match, ignore the UID match
and remove the Guid detail from one contact.

Also restore pre-fetching of favorite contact details.

Extract SeasideCache from nemo-qml-plugin-contacts and export from
this library.