added streaming/file-per-process/default modes to adios output in performance test
adios_transform_parse_spec can use existing struct to fill in (or allocate new one)
removed adios_group_struct from var size calculation functions (in transform layer)
adios_transform_get_metadata_size() returns 0 size on NULL ptr transform spec
- added adios_set_transform() to non-xml write API
- removed adios_group_struct from var size calculation functions
fix: transform test to call var size function with correct arguments
added transform to some examples (in XML or call adios_set_transform in non-XML examples)