Added empty values in unused but required tags in gdcmSurfaceWriter. 

Hi there,

According to the Surface Mesh Primitives Macro (Table C.27-4 of the DICOM standard), the Surface Mesh Module must contain the following tags : 
- Vertex Point Index List 	(0066,0025) - Type 2
- Edge Point Index List (0066,0024) - Type 2
- Triangle Point Index List (0066,0023) - Type 2
- Triangle Strip Sequence (0066,0026) - Type 2
- Triangle Fan Sequence (0066,0027) - Type 2
- Line Sequence (0066,0028) - Type 2
- Facet Sequence (0066,0034) - Type 2

The current implementation of gdcmSurfaceWriter only writes the tags needed to store the data. 
This patch adds the writing of the tags that are required by the standard but not necessarily needed to store the data.

Thanks,

Clement