Revision 594571

Moved the creation of grid units to the FO tree building stage. Brought a few improvements along with the move:
- bugfix: border-resolution for border-end on row-spanning cells was wrong
- bugfix: in case of missing cells the border-end of the table was applied to an inner cell, instead of the cell in the last column (but missing cells aren't painted yet :-\)
- bugfix: in collapsing-border model, border-before and -after specified on table-column were applied to every cell of the column, instead of only the first and the last ones
- border resolution is now made progressively when possible, and no longer triggers the fetching of all the rows of the table
Added testcases for the border conflict resolution (between the various elements of a table and not only the cells)