Resolve duplicate README files in packages

In Qt 4 source packages, the README file in the root directory of the package came from dist/README (now qtbase/dist/README in the Qt 5 repo).

In the Qt 5 source packages, the README file in the root of the package comes from somewhere else and qtbase/dist/README stays in that location, where presumably few people will ever read it.

The two README's should probably be merged. Ideally README would live in the same place in both source packages and the repo so that the pacakging scripts don't needc to move the file during packaging (which was the case for Qt 4).