When reading in docx documents, fine dashing provides a better visual
match for some border types.
Added in this patch:
 - FINE_DASHED in BorderLineStyle UNO enum and in internals
 - Import of docx table borders using this border style

Change-Id: I39cfa18c915ec94d8e4ecfc6a2ca637076d1e468
Reviewed-on: https://gerrit.libreoffice.org/1123Reviewed-by: Fridrich Strba <fridrich@documentfoundation.org>
Tested-by: Fridrich Strba <fridrich@documentfoundation.org>