Mac Core Text font database for QPA

Mac Core Text font database for QPA

Add Core Text fontdatabase for Mac and use it as default. It also
reenabled Core Text font engine for native font rendering on Mac,
though it's not used in declarative UI (by default declarative
will still use scenegraph, which will only use this font engine
for retrieving font metrics and outlines).

With the new fontdatabase it's now possible to load all the fonts
installed in the system as well as adding application fonts.

Change-Id: I0d2aa1420019adf6d0f70dd147a9d71b2684d3f1
Reviewed-by: Morten Johan Sørvig <morten.sorvig@nokia.com>