Extended XLineColor to handle model::ThemeColor which then maps
to the newly added LineColorThemeData property.
Extended oox import and export to map the scheme color elements
to and from ThemeColor. Added a new test to check the theme line
color in impress shapes.
Change-Id: I23ecc18c88b5b47608c9110f5681f189d02e2f36
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/145071
Tested-by: Jenkins
Reviewed-by: Tomaž Vajngerl <quikee@gmail.com>
