[qtcontacts-sqlite] Ensure incidental contact is linked into aggregate

Previously, if a single write caused both a modify of an existing
synctarget constituent plus the creation of a new incidental contact,
the incidental contact would not be linked into the appropriate
aggregate via a relationship.
This commit ensures that the incidental contact is always linked
correctly.
Merge pull request #115 from chriadam/fixincidental

[qtcontacts-sqlite] Ensure incidental contact is linked into aggregate
[qtcontacts-sqlite] Remove childless aggregates after applying sync delta

This commit ensures that if any synctarget constituents are removed
as a result of a sync operation, that any aggregates which are made
childless as a result of the operation are also removed.
Merge pull request #116 from chriadam/removechildless

[qtcontacts-sqlite] Remove childless aggregates after applying sync delta