* Updated source file copyright headers to remove "Copyright by the Board of Trustees
of the University of Illinois", which is kept in the top-level COPYING file.
* Modify temporary rpath for testing in java example scripts.
* Update URL in source file Copyright headers for web copy of COPYING
file - src and test directories.
1. switched to use the existing H5F_prefix_open_t for enum type;
2. put the common private function used by external.c and external_env.c into external_common.c
1. restored the datatype, dataspace, and LCPL of the dataset for VOL connector back to the properties.
2. splitted external.c and vds.c because they called HDsetenv in the program, instead using shell scripts to set the environment variables.
3. changed H5CX_get_vds_prefix and H5CX_get_ext_file_prefix to use H5P_peek instead of H5P_get.