[contactsd] Remove dual build, make Qt 5-only.

There is no real sense in having this dual-buildable. The only point would have
been as a library is provided for out-of-tree plugins. But only one contactsd
can run at once, and (outside Nokia), no out-of-tree plugins exist.
[contactsd] Add some missing build requirements
[contacts] Remove confusing diff from Qt 4-to-5 port.
Merge pull request #10 from rburchell/master

Make Qt 5-only.