Further dataflow visualisation enhancements

[anjackson]

• Allow places to include 'boundaries', and use the underling library to snake a 'river' through the diagram.
• add 'domain' to places and switch the river there, maybe adding a "pseudo line" vertical to make that clear? Adding a domain adds a line along the side, adding a next domain adds a river, switches sides. So adding boundaries, in effect. Use community as bounds
• The shiftCoords currently forced to be the same for both ends of a move/copy, which makes some alignments difficult. Need some way to let the start be the same as the parent, but then the final shift be different.
• Start/end labels not working very well. End labels work fine if there's no start. Maybe use a different approach to laying out the locations on the 'in' side. (on the suggested domain bracket instead).
• changes to the 'simple text markup':
  • Allow space/time spacing to be changed in the workflow config.
  • markerShiftCoords could maybe be a reinterpretation of `@N@0.5I?
  • interchange is automatic, for 'transform' and 'delete' events only. Maybe extend the @N@0.5+I syntax?