Harmonize GridLayout2 and GridData2 with SWT classes

[ptziegler]

Similar to #963, the GridLayout2 and GridData2 are old copies of the SWT layouts, which store additional information that are relevant during design time.

We should separate the designer information from the layout algorithm to make sure that our implementation matches the actual implementation.

[ptziegler]

To summarize: WindowBuilder defines the following fields:

• int[] m_columnOrigins, for each column, contains the x coordinate of the left edge
• int[] m_columnWidths, for each column, contains the width
• int[] m_rowOrigins, for each row, contains the y coordinate of the top edge
• int[] m_rowHeights, for each row, contains the height
• Map<Control, Point> m_controlToXY, for each row, contains its position in the grid

The position is probably the easiest to calculate on-the-fly. The layout already specifies the number of columns. The number of rows can then simply be calculated by the number of widgets divided by the number of columns, rounded up.

e.g. with 5 widgets and 2 columns, the number of rows is ⌈5 / 2⌉ = 3.

The position for each widgets can then simply be determined by iteration:

• (0,0) (0,1) (1,0) (1,1) (2,0)

The width of a column is the max. width of all containing widgets and similarly the height of a row is the max. height of all containing widgets.

The origin of a column is the min. x coordinate of all containing widgets and similarly, the origin of a row is the min. y coordinate of all containing widgets.