BUG-FIX: on signal window close _disconnect instead of navigator was called
Rename drawing.image.Image.update_image -> update
Image was not disconecting AxesManager on close
Signal.swap_axes now returns a copy of the object instead of operating in place
Add file_format and file_format_version to the hdf5 file
An exception was raised on start when netcdf was not installed
BUG-FIX: Image was raising an exception when axes_manager was not defined and connect/disconnect was called
BUG-FIX: load signal_type, record_by and signal_origin were not overriding the values in the file. Also several improvements to the docstrings and to the exceptions raised when a wrong value is passed to any of these arguments