Improve Table-Rendering "adjust to grid" and "avoid faulty table layouts"

     Current Table-rendering in some cases (rowspanned cells, cells with different baselines) is not capable of fixing slightly overlapping elements properly leading to disappearing lines
     Also the current algorithm of calculating rowspans fails in situations, where a cell starts AND ends "in the middle" of other rows
     faulty table-layouts/rowspans often lead to ugly rendereing-problems ("exploded" tables)
    New Algorithm:

• Scanning the table top to bottom before rendering
• Insert rowspans for the other elements "touching the line" whenever an element starts or ends "in the middle" of other elements (not on-line)
• Add checks to slightly reposition elements to the left/right/top/bottom in case they overlap their predecessor or left/right neighbour. The relocation can be achieved using the "Collision-Map" from feature https://jira.translate5.net/browse/TRANSLATE-4106
• in case elements can not be repositioned add negative margins and shrink the element to fit: This leads to visible overlaps in the frontend but keeps the overall layout