schemas/VegCore/VegCore.ERD.mwb: moved all required fields before optional fields

schemas/VegCore/VegCore.ERD.mwb: regenerated exports and udpated image map

schemas/VegCore/VegCore.ERD.mwb: individual: identifying_place: documented that for specimens, this is the place the specimen was collected at. within_place: documented that this is not specified for specimens since their coordinates are usually not precise enough to identify an individual. specimen: documented that when there are multiple specimen replicates (copies) of a specimen, each gets its own specimen_observation pointing to the same specimen.

schemas/VegCore/VegCore.ERD.mwb: individual: added identifying_place since some individuals may be identified by their coordinates rather than a tag

schemas/VegCore/VegCore.ERD.mwb: added back aggregate_observation as a superclass of taxon_absence, taxon_presence. have only aggregate_observation, not taxon_observation, inherit from taxa_sampling_event because taxa_sampling_event is designed for multiple or aggregate samplings, but taxon_observation can be for just one occurrence. taxa_sampling_event: added required within_place since taxa must be sampled within a particular place. individual.place: renamed to within_place to clarify that each individual does not necessarily need its own place instance. individual_observation: added place_observed_at to serve the role that individual.place previously did (the place of an individual may change between observations).

schemas/VegCore/VegCore.ERD.mwb: aggregate_observation: renamed to individual_count for clarity. added count field. renamed traits to aggregating_traits since these are used in uniquely identifying the individual_count. taxon_presence: added cover_percent.

schemas/VegCore/VegCore.ERD.mwb: taxon_presence: documented that this is actually equivalent to VegX's aggregateOrganismObservation ("An observation applying to all occurrences of an organism"), in spite of VegCore having its own aggregate_observation table with a different purpose

schemas/VegX/.htaccess, TCS/.htaccess: prepend / to subpath so that it becomes an absolute XPath. the subpath is now usually provided as a dotpath translated to a dirpath, which would not have a leading / .

fix: schemas/VegCore/VegCore.ERD.mwb.run: comment about why the Mac version does not export the PDF correctly: clarified that it is the single-page PDF where the lines take very long to load, and the printed PDF where the colors are wrong in Adobe Reader

schemas/VegCore/VegCore.ERD.mwb.run: documented that to edit VegCore.ERD.mwb, you must use the Linux version of MySQL Workbench. this is because the Mac version does not export the PDF correctly: the colors are wrong in Adobe Reader and the lines take very long to load. unfortunately, you also cannot switch back and forth between the two versions, because they render the lines with a different spacing, which makes the tables different sizes and misaligns the connector lines. it is especially unfortunate that the Mac version messes up the PDFs, because it uses a smaller line spacing and therefore smaller tables which allows the tables to be spaced farther apart for better readability.