Full colour borders in .doc import/export

The BRC (BoRder Control) structure used in .doc files to specify border
properties has undergone several revisions over time.  LibreOffice
supports the WW6 and WW8 (Word '97) BRC versions, which allow the border
colour to be selected from a palette of only 16 colours.

This changeset adds support for the WW9 (Word 2000) BRC version, along
with some new SPRMs (Single PRoperty Modifiers) which use it, so that
border colours are preserved accurately in .doc import/export.

This change covers:
- page borders
- paragraph borders
- borders around a sequence of characters
- table / table cell borders (import only)

Further work is required to extend coverage to borders of pictures and
export of borders in tables.

The LO code was using the same class WW8_BRC to store the bits for either
the WW6 or WW8 BRC.  This becomes a bit unmanagable when adding a third
BRC version, so I have split this into a separate class for each version.

Fixes fdo#68475, fdo#50185

Change-Id: I7ebc15236497cbab9312d8659fe7ed0bee2c59ed
Reviewed-on: https://gerrit.libreoffice.org/8646
Tested-by: LibreOffice gerrit bot <gerrit@libreoffice.org>
Reviewed-by: Miklos Vajna <vmiklos@collabora.co.uk>