use integer dpi values when retrieving ArcGIS vector tiles
change server params and later recipes to YAML format; move some server parameters to layer options instead
refactor vector layer rendering options
change location for specifying contour interval
move default rendering settings into layers recipe
check for controls file properly
handle ArcGIS layer names with spaces
add alternate contour source
change contour interval option (again)
add alternate topographic layers
add option to pretty-print SVG
add backup source for alt-labels
update history
revert to flat layer structure for SVG file
save empty ArcGIS layers but don't tag as groupmode:layer
change HydroArea layer to perennial water areas only
only re-render non-empty layers