Merge branch 'compression_tests' into 'master'

doc/RTD/source/ParameterFiles/index.rst

doc/RTD/source/ParameterFiles/lossy_filters.rst

doc/RTD/source/ParameterFiles/output_selection.rst

doc/RTD/source/ParameterFiles/parameter_description.rst

src/Makefile.am

src/common_io.c

src/distributed_io.c

src/io_compression.c

src/io_compression.h

src/io_properties.h

src/output_options.c

src/output_options.h

src/parallel_io.c

src/serial_io.c

src/single_io.c