[libcommhistory] Use QtContacts API for contacts updates if configured

To select the QtContacts API for updates/retrievals, alter the DEFINES in:
    common-vars.pri
[libcommhistory] Allow qtcontacts backend to perform phone number normalization
[libcommhistory] Ensure contacts order is preserved

Return contacts to match the order found by tracker, rather than the
order in which they're returned by QContactsManager.
[libcommhistory] Compare phone numbers in minimized form
[libcommhistory] Filter out relationships from contacts query

Relationships are very expensive and are unused.
[libcommhistory] Remove conditional compilation of QtContacts code

Sparql-based version is no longer provided.
[libcommhistory] Cache resolved contacts within a query

The models tend to resolve numerous events for a small set of contacts
within the scope of an executed query.
Merge pull request #15 from matthewvogt/qtcontacts-api

[libcommhistory] Use QtContacts API for contacts updates if configured