select nsw/topographic as default map
make label options more descriptive
refactor labelling code
tweak
automatically group features by class
add preliminary line-feature labelling
add Array#rotate_by_angle
add Array#to_path_data
fix rotation sign error when testing line-feature direction
sort line label candidates according to smoothness
don't use tspan dy attribute to shift line labels
check for candidate label proximity across line ends
change label-by to assume category
tidy-up
improve label conflict resolution performance
improve variable naming
add some line-feature labels