Tests for the new implementation of the qx.ui.layout.HorizontalBoxLayout widget.

1. Simple testing, one static and one flex child
2. Two flex children with the same priority
3. The same as #2, but the second has the doubled priority compared to the first

4. The same as #3, but now the second child has a max-width of 50px
5. The same as #4, but now with enabled "advancedFlexAllocation"

6. The same as #3, but now the second has a min width of 500px
7. The same as #6, but now with enabled "advancedFlexAllocation"

8. Three children with the priorities: 1, 2 and 3. The second has a maxWidth of 50px
9. The same as #8, but now with enabled "advancedFlexAllocation"

10. Three children with the priorities: 1, 2 and 3. Added a few mouse actions.
11. Three children with the priorities: 1, a static width of 80px and 3.
12. The same as #11, but configured as 'auto' width.

13. Test for more complex child widgets. Seems to work without problems.