Version 0.6.0

• Improve property handling and introduce derived properties
  • Drops xplt.units module in favour of xplt.properties
  • Drops xplt.register_property method in favour of xplt.register_data_property and xplt.register_derived_property
  • Drops wrap_zeta=True keyword argument in favour of property zeta_wrapped
  • For details, see https://eltos.github.io/xplt/examples/properties.html
• Improved consistency
  • Make pandas an optional dependency
  • Renamed metric= keyword argument of TimeVariationPlot to kind=

Full Changelog: v0.5.0...v0.6