mapsf_0.9.0

Fix

• add the possibility to use a scale bar in (US) maps using feet based CRS (#59)
• deprecate unit argument in mf_scale()
• remove wrong ellipsis propagation in mf_label()
• better environment management in mf_legend() to allow usage inside a
  function (#58)
• fix raster legends (using type arg, see feat.) (#60)

Feat

• add "interval", "continuous" and "classes" types with matching legends in
  mf_raster() (#60)
• mf_raster() invisibly returns the initial raster