How to rename the project and also its files?

I think the easiest way I found to do it in the past if you only have one project revision is follows. (I can't remember exactly as it was a couple of years ago, so make sure you have a backup copy of your project before proceeding)

(1) Make a new revision in the project with the new name you want, making sure you ask for all of the files to be copied from the current one.

(2) Delete the original revision leaving just the new one.

(3) Close the project.

(4) Manually rename the project folder and the ProjectName.qpf file to be the new name.

Then if you open the project again, it should be renamed. All of the output files and intermediate files get renamed when you make a new revision of the project so it should just be the folder and .qpf you have to do manually.