nabu_processes.h5: conflict when using with several datasets

Sometimes there can be several datasets (.nx files) in the same directory, with at least two of them sharing the same HDF5 entry (eg. entry0000).

$ls /path/to/datasets
dataset1.nx
dataset2.nx
dataset3.nx
...

In this case, a nabu_processes.h5 will be generated for the first .nx dataset, and then it will be (wrongly) re-used for all the other datasets sharing the same HDF5 entry.

Assuming this use case is legitimate, there are at least two solutions:

1. Robustify the loading of nabu_processes.h5, so that the content is loaded only if the dataset matches the correct prefix
2. Add the dataset prefix in the file name, ex. dataset1_nabu_processes.h5