Fixing various issues regarding export-import round-trip. Refs #19523.
Preparing XML Schema for EMERALD. Refs #19831.
Preparations for the validation and export-import round-trip of EMERALD sites. Refs #19523.
Preparations for the validation and export-import round-trip of EMERALD sites. Refs #19523.
Merge branch 'master' into roundtrip_19523

Conflicts:
	src/main/java/sdf_manager/ExporterMDB.java
	src/main/java/sdf_manager/SDF_ManagerApp.java