More flexible project files and options

[Ri0n]

It would be nice to have *.pri with al the logic inside which could just be included into upper level project to compile and link everything with upper level project.
The same *.pri file could be used by qhttp.pro or src.pro to compile shared library.
So all compilation logic in *.pri file and all project/installation logic in *.pro file.

Then it would be good to have some option to switch static/shared library compilation.