replace remaining instances of ScientificSpinBox and QDoubleSpinBox by DoubleSpinBox

If necessary, we will make DoubleSpinBox configurable to serve different needs. But we don't want three classes and three different APIs for basically the same purpose.

First steps:

  • replace ScanProperty by AxisProperty, ScanForm by AxisForm (#1001 (closed))
  • reconcile BasicAxisItem with AxisProperty
  • replace ScanRangeForm by AxisForm
Edited by Mikhail Svechnikov