Hdf2Xdf: convert hdf datasets into xdf datasets

Convert hdf5 files to xdf files.

Use:

Hdf2Xdf [-h] [hdfdir] [xdfdir]

When directories containing the hdf files and directories where the xdf should go are not given,
pop-up selection tools appear:
  - select the approprate files interactively (multiple file selection allowed).
  - select the directory to which to write to the xdf data file(s).

Otherwise provide the directories with the hdf (.h5) files and the
directory where the xdf files should go

Both I and Q data are written into the xdf file.