v0.3.0

Various fixes for 4.2
Added NodeUtils.connect_signal_safe().
Added Area3D.svgdefault icon.
Added Area3DPreferredObjectPicker.
Added editor functionality for FloatingOrigin.
Added option to disable FloatingOrigin shifting on Y axis.
Added option to disable plugin singletons in project settings (disabled by default).
Added NodeUtils.get_descendants_of_type().
Added NodeUtils.has_node_of_type().
Added NodeUtils.get_first_child_of_type().
Added NodeUtils.get_first_descendant_of_type().
Renamed NodeUtils.get_first_parent_which_is_a() to NodeUtils.get_first_parent_of_type().
Added MathUtils.log_with_base().
Added Point3D.
Updated Vector3D.