Rafactor model: Rename some functions to be consistent with other names

During the overhaul of the instrument view it was noticed that some member functions have a different way of being named than others. This MR renames two functions so that they are more consistent with other function names: in SpecularBeamItem currentInclinationAxisItem becomes inclinationAxis and currentFootprintItem becomes footprint.

requested review from @m.puchner

assigned to @m.puchner

approved this merge request

assigned to @t.knopff and unassigned @m.puchner

mentioned in commit 3b541411

merged