Build/install kdreports like a Qt module

[frankosterfeld]

Nicolas: "We may want to simplify [the installation/deployment] a bit, and create a sort of Qt module, with make install putting everything in the Qt directory."

[dfaure-kdab]

This would be problematic on Linux, when Qt is in a non-writable directory (/usr). So we would have to support other means of installation anyway - and therefore adding the "qt module" way would just mean one more case to support....