DrawIO DSL

add help messages when invalid lookups are used for stroke, design etc.

settings style attributes need to de-duplicate, might be best to utilize the new StyleBuilder class

line connectors attributes for :strokes (done), compass_points, designs, arrows and waypoints

line connector aliases gives a simple way to use predefined line configurations

line connectors need to support autolinking using ids

line connectors should not effect the grid positioning systems

new format for connectors - connect(:a, :b, :solid)

bg_theme does not work

improve coverage

class html builder to support include/extend modules, class methods