Refactor PdmUiOrdering::LayoutOptions

[magnesj]

Use of Layout options in PdmUiOrdering is difficult and the default constructor hides the names of the struct members. This makes the client code difficult to read and understand.

Suggestion

Move MAX_COLUMN_SPAN to PdmUiOrdering
Avoid default constructor, add initializer

    static const int MAX_COLUMN_SPAN = -1;
    struct LayoutOptions
    {
        bool newRow {true};
        int  totalColumnSpan{MAX_COLUMN_SPAN};
        int  leftLabelColumnSpan{MAX_COLUMN_SPAN};
    };