Backport CMS7 8409 to 7.9 - Autoexport creates incorrect (too low) sequence number for file in control of the project

The auto export module incorrectly creates a too low sequence number for changes that are within the project scope. This is the second time I run into this issue. I've experience this with the latest 7.9.3 release and the getting started archetype (essentials).

The reproduction path is quite simple:

1. Create a project based on the archetype http://www.onehippo.org/trails/getting-started/creating-a-project.html
2. Build and run the project
3. Add a node of type hst:component with the name 'test' to the /hst:hst/hst:configurations/common/hst:components
4. Save the changes.
5. You will see in the hippoecm-extension.xml that there is a new initialize item with a sequence node of 30000.3 while the parent node in the configuration is at 30055.

This is really annoying for new developers that don't know yet about the sequence numbering. Changing it manually will fix it of course, but it would be great if the auto export can just take a higher number then the highest number in the hippoecm-extension.xml file(s).