Export/Import site while keeping the 'unpublished' flags

Problem: Moving content to a new OpenCms VFS that is not published and unchanged completely but has changes / new files that must not be published when migrating the content to a new OpenCms.

The solution was written by Michael Emmerich on the OpenCms Mailing list opencms-dev@opencms.org on November 18th 2009. Credits:

when you want to migrate from OpenCms 6 to 7 as well, you should try the 
following:

1) Go to the ONLINE project and export your content with the Database 
Adminstration. This will make an export file that only contains the 
content that was already published.

2) Now switch to the project where you have made the changes that are 
not published yet. In the Database Adminstration, mark the checkbox 
"Changed in project". This should only export those files that are 
changed or new in the current project you just have selected.

You then have two export files. Import the first one in your new system 
and publish everything.
Then create a project for the the unpublished files, switch to it and 
import the second export fiel you made.

If you want to migrate modules, you MUST always do this with the module 
export/import. You can later add changed module resoruces as described in 2)