[qtcontacts-sqlite] Fix birthday duplicate handling

Previously, birthday details were not treated as unique details.
This commit ensures that they are dealt with properly during
aggregation.
Merge pull request #33 from chriadam/birthday

[qtcontacts-sqlite] Fix birthday duplicate handling
[qtcontacts-sqlite] Use separate indexes for independent properties
Merge pull request #34 from matthewvogt/index-fix

[qtcontacts-sqlite] Use separate indexes for independent properties