[libcontacts] Allow empty avatar to precede others with multiple avatar types

If a contact has avatars with multiple metadata types, a non-empty
type would still override an empty path for a preceding metadata
category.
Merge pull request #44 from matthewvogt/empty-avatar

[libcontacts] Allow empty avatar to precede others with multiple avatar ...
[libcontacts] Ensure contacts are not in name groups on cache removal
Remove superfluous group validity tests
Merge pull request #45 from matthewvogt/removal-notification

libcontacts] Ensure contacts are not in name groups on cache removal
[libcontacts] Fetch modified contacts after link/unlink
Merge pull request #46 from matthewvogt/fetch-after-agg

[libcontacts] Fetch modified contacts after link/unlink
[libcontacts] Only index non-empty address elements
Merge pull request #47 from matthewvogt/index-non-empty-addresses

[libcontacts] Only index non-empty address elements
[libcontacts] Only index valid phone numbers
Merge pull request #48 from matthewvogt/only-index-valid

[libcontacts] Only index valid phone numbers
[libcontacts] Increase the maximum digits used in minimized phone numbers

Although 7 digits is typically enough to differentiate phone numbers
in their local forms, an eighth digit is sometimes required to
differentiate between a local number and the voicemail service for
that number.
Merge pull request #49 from matthewvogt/max-digits

[libcontacts] Increase the maximum digits used in minimized phone number...
[libcontacts] Move import logic to libcontacts for sharing

Should be used by the batch importer and the GUI importer.
Merge pull request #50 from matthewvogt/importer

[libcontacts] Move import logic to libcontacts for sharing
Update exported library version
[libcontacts] Name grouper fixes.

Allow grouper to override default set of groups. Ensure
returned group is in the valid list of groups.
Merge pull request #51 from mbrasser-jolla/master

[libcontacts] Name grouper fixes.
[libcontacts] Allow multiple matches for a minimized phone number

For resolution, find the contact possessing the number with the longest
match to the input number.

Also, correct the previous terminological misuse of 'normalization'
to mean 'minimization'.
[libcontacts] Select best match from resolution request results