Introduce QmakeParser*FileNodes by copying Qmake*FileNodes and renaming
things so that nothing conflicts and both sets of Nodes can be built at
the same time.

The goal of this patchset is to disentangle the project parsing from the
project structure as shown in the project tree.

Change-Id: I4e7383b71849ed4de15d29a45c9b249aa2319a27
Reviewed-by: Tim Jenssen <tim.jenssen@qt.io>