v0.3.0

Added

• [interface] singleton DEFAULT for storing and controlling default parameters.
• [interface] 3d surface plotting: figure.surface3d(...)
• [color] class ColorScroller for maintaining automatic color switching for plotting.

Changed

• [engine] the engine management system reworked: engine.get(), engine.available(), engine.register().

Fixed

• [engine.plotly5] legend item width increased to show dashed line correctly.
• [engine.matplot] problem with figure.close() fixed.