Improve column names for disp

[LukasBeiske]

• This removes the disp_parameter_is_valid column, since it is identical to the disp_tel_is_valid column.
• Doing this makes it possible to use the same prefix for both the DispContainer and the ReconstructedGeometryContainer, as filled by DispReconstructor.
• As the DispContainer contains the output values of both the regressor (norm) and the classifier (sign) as a single value (sign * norm), I renamed this value to "parameter" to avoid confusion.

HOWEVER: DispReconstructor still creates all the geometry-related columns contained in ReconstructedGeometryContainer even though it only computes altitude and azimuth. But since the creation of such empty columns is not limited to the disp reconstructor, I think it would be better to address this in a different PR.

[maxnoe]

Related: #2228

We could have a ReconstructedDirectionContainer, a ReconstructedImpactContainer and a ReconstructedGeometryContainer that combines the first two for algorithms that do all on one go.

[maxnoe]

The changes look good to me, but this requires a bump in the data model version,
an entry in the data model changelog and probably dropping support for reading older files.

[maxnoe]

And some tests and more code has to be adapted, see the test failures.