fix an OOXML chart validation error

Change-Id: Ic91f6179b663afb59700f85ea48720dc9b14f372
fix an OOXML chart validation error

Change-Id: I0c95aa285509187b6d54f44c41720e2aefab175b
fdo#72306 Axis names were lost after saving file on LO.

  While exporting chart "crosses" position values were
  not handled properly in chartexport.
  Fixed this issue by handling "autozero" value for c:crosses.
  Added unit test.

Change-Id: I3489908d4c3d4b41a04debfecf95e65f373649ce