Better hdf attributes
Created by: SkyToGround
Description of work
- All writer modules now set a NX_class value.
- The NX_class value configured for a writer module will always override that of the HDF group NX_class value. If configured, a writer module attribute (e.g. NX_class) will override both.
- The Kafka topic and flatbuffer source names will now automatically be written as (HDF) attributes when instantiating a new writer module.
- Minor fix to CMake code for working around issues caused by differences in how file-name leading lower and upper case letters are handled on different systems.