Pninexus

- creating string arrays with an empty dimension fixed ([132](https://github.com/pni-libraries/libpniio/pull/132))
- checks if field/group exist ([133](https://github.com/pni-libraries/libpniio/pull/133))

- HDF5_version attribute changed to HDF5_Version ([121](https://github.com/pni-libraries/libpniio/pull/121))
- NeXus_version attribute removed ([121](https://github.com/pni-libraries/libpniio/pull/121))

- string are stored in the scalar dataspace by default ([115](https://github.com/pni-libraries/libpniio/pull/115))
- xml_to_nexus: when data is not provided a field of rank 1 and size 0 is created by default ([31](https://github.com/pni-libraries/libpniio/pull/31))