qbs build: Get rid of CopyTransformer.

That item was using a directory as an output artifact, which was only
working by accident and often caused warning messages about failure to
remove files.
Use a proper module instead, which is the nicer solution anyway.

Change-Id: Ib75a0ce26a24c78eb5421367995a8fc72f6a3c2a
Reviewed-by: Joerg Bornemann <joerg.bornemann@digia.com>
QbsProjectManager: Only update project nodes etc if necessary.

That is, if qbs::Project::projectData() has changed. There are still
some false positives left (e.g. the project nodes will also update if
only the file paths of executables have changed), but we can deal with
those later.

Change-Id: Ifa18903aba41c21769bfe4cd0e4f6004f1a94f11
Reviewed-by: Joerg Bornemann <joerg.bornemann@digia.com>
QbsProjectManager: No more "forced" vs "non-forced" parsing.

This differentiation complicates the code and duplicates checks
already done in qbs.
Just let the library reparse the project; if it turns out that nothing
has to be done, then the operation will be fast.

Change-Id: Ib6406f254e51541c69c948f275fff7877b65b4bd
Reviewed-by: Joerg Bornemann <joerg.bornemann@digia.com>