added schemas/VegCore/document.mwb.xml, so changes to the diagram can be tracked line-by-line. keeping this up-to-date requires running `unzip VegCore.ERD.mwb document.mwb.xml` whenever VegCore.ERD.mwb is changed.
added schemas/VegCore/document.mwb.xml, so changes to the diagram can be tracked line-by-line. keeping this up-to-date requires running `unzip VegCore.ERD.mwb document.mwb.xml` whenever VegCore.ERD.mwb is changed.