support gdal /vsi* in wcst_import and petascope

[Dimitar Misev]

I attached a test ingredients which should be added to test_all_wcst_import, attachment:wcps_rgb_gzip.tar.gz​

Problems to be fixed:

• convert relative path /vsigzip/rgb.png.gz to absolute path somehow in the systemtest; maybe add CURRENT_ABSOLUTE_DIR support in the templates

  /vsigzip//home/rasdaman/systemtest/.../rgb.png.gz
  

• petascope seems to change // to /, e.g.

  /vsigzip//home/rasdaman/systemtest/.../rgb.png.gz
  is converted to 
  /vsigzip/home/rasdaman/systemtest/.../rgb.png.gz 
  

  which fails to import