fdo#41034 improve RTF import of table cell spacings
fdo#41034 improve RTF import of table cell spacings

1) for empty cells, not only paragraph properties, but but character properties should be emitted as well (e.g. font)
2) \sb and \sb is an attribute, not an sprm (it was ignored)
3) \sl was ~ignored due to a typo

JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core