o Speed up drawing of tables

Calling format.properties() is very expensive. This is done in the constructor of
KoTableCellStyle. And that is called when painting each cell border. However the
data is not needed to paint cell borders. Therefore the class KoTableBorderStyle
which handles the drawing of the borders has been created. KoTableCellStyle inherits
this class.
This removed quite a lot of unneeded calls for document with tables.