Merge project options

[jtgilbert]

It would be nice if there was the option to select e.g., just vector datasets, or just a single dataset or geopackage when running the merge projects script to save on time and space if you don't want big datasets like the DEMs merged.

[philipbaileynar]

That's not too hard... just need to think about the syntax. Maybe use a list of XPaths to the desired items.