Fix for: DOCX-Preservation of Line style Dash type of "Shape with text inside"

    Issue :
        File containing Shape with text inside it having Line style as
        Dash type is not getting preserved after RT in MS office 2007.

    Implementation :
        1] Added XML element <v:stroke> with attribute  dashstyle="dash".
        2] Written Export Unit test case.

Conflicts:
	sw/qa/extras/ooxmlexport/ooxmlexport.cxx
Reviewed on:
	https://gerrit.libreoffice.org/7611

Change-Id: Id01c5975c2c1cf176a7459f65973f4c9c3c9b9d8