mappings/VegCore-VegBIEN.csv: event__participant: allow multiple event__participant columns

mappings/VegCore-VegBIEN.csv: project_participant: use [!...] negative lookahead assertion so that multiple project_participant columns will properly map to separate projectcontributor rows

moved everything into /trunk/ to create the standard svn layout, for use with tools that require this (eg. git-svn). IMPORTANT: do NOT do an `svn up`. instead, re-use your working copy's existing files with `svn switch` (http://svnbook.red-bean.com/en/1.6/svn.ref.svn.c.switch.html).

mappings/VegCore-VegBIEN.csv: mapped project_participant

mappings/VegCore-VegBIEN.csv: mapped taxon_determination__is_current, taxon_determination__is_original

bugfix: mappings/VegCore-VegBIEN.csv: main taxondetermination: use [!isoriginal=true] instead of [!isoriginal] so that adding a manual isoriginal field does not prevent this selector from matching

bugfix: mappings/VegCore-VegBIEN.csv: nest all taxonoccurrences inside a stratum event, so that the parent locationevent is always fully populated before child locationevents point to it. (previously, a stub parent event was created when the child event was imported first, which blocked the fully-populated parent event from being inserted later on.) this uses auto-folding (for VegBank/CVS) and auto-forwarding (for other datasources) to prune empty stratum events for taxonoccurrences that don't have strata. (see wiki.vegpath.org/Auto-folding, wiki.vegpath.org/Auto-forwarding for more info about these normalization techniques.) note that the inserted row counts stay exactly the same for all datasources except VegBank (which was being fixed), indicating that this signficant change to the mappings did not change the semantics of the import of taxonoccurrences.

bugfix: mappings/VegCore-VegBIEN.csv: stratum's locationevent: link this to the parent locationevent, so that the parent locationevent's information (such as locationeventcontributors) is accessible to the stratum's locationevent

mappings/VegCore-VegBIEN.csv: mapped event__participant

mappings/VegCore-VegBIEN.csv: mapped stratum__name