bnc#882627: Allow to edit spacing to contents even with no borders visible.

SfxItemSet::MergeValue changes some items from SFX_ITEM_DEFAULT state to
SFX_ITEM_SET which I think is a bug but this patch avoids the problem too.
The issue was: visible changes in some tables, after changing e.g.
borders spacing, because the cells had wrong SfxItemSet after the process.

Change-Id: I676b211e1a4a1d7341c385d63503aa740718ed5d
(cherry picked from commit b1d8df61b47e84bf0de64342556049673dd9c543)
Signed-off-by: Andras Timar <andras.timar@collabora.com>
bnc#882631: keep line visible if proportional line spacing is < 100%.

If line height is smaller than text height, we still want to see whole first
line, so add the difference where necessary.

This also helps to see paragraphs as separate to each other.

Change-Id: I51a87edf0cc03d5b5e130290c90347099a581d4e
(cherry picked from commit e42c05c1f96832572e525d85d89590f56f5a29dd)
Signed-off-by: Andras Timar <andras.timar@collabora.com>