Nexusformat

- This fixes a bug, in which a NXfield that is stored within an existing NeXus file is copied to another group stored in memory, and then that group is copied back to the original file. If the NXfield is large, this caused the file to be closed before a file update is completed.

- Linked items within a file can now have different names from their target. This restriction was lifted a few years ago.
- Added a compression filter setting, NX_COMPRESSION, which defaults to 'gzip'. This can be set using the nxsetcompression function, _e.g._, `nxsetcompression('lzf')`. It can also be set to ‘None’.
- Added a unicode encoding setting, NX_ENCODING, which defaults to 'utf-8'. This can be set using the nxsetencoding function, _e.g._, `nxsetencoding('latin1')`.
- The nexusformat package now uses variable length strings for storing all text fields using utf-8 (the h5py default), but fixed length strings in existing files could have a variety of encodings. If there is a decoding error when reading a string, nexusformat will see if 'latin1', the most common alternative, works. However, there is no guarantee that the correct encoding will be selected.
- The `nxtree` function has been renamed `nxdir`, to prevent clashes with the NeXpy GUI.
- Improved handling of infinities when plotting.
- Improved copying of large datasets between files.
- Improved handling of singleton and reversed axes.
- Fixed a bug that caused a shift when slicing data whose axes are stored as bin boundaries rather than centers.
- Added a `__nonzero__` function to NXfield. Note that this means that if statements involving the NXfields will return False if all items are 0 and True otherwise.

- Now supports plotting of RGB(A) image plots, with the new 'implot' method.
- Moved plot methods into NXdata class. This will allow plotting in NXmonitor and NXlog classes as well. If you attempt to plot another class, it will search for a valid NXdata group within its hierarchy.
- Individual NXfields also have a plot method. They will be plotted against default axes.
- Allow the plotting axes to be defined by an attribute array, as well as a single delimited string.
- Removed the NeXus version number from the file attributes when creating a new file. This version number used to refer to the C-API version, but that is no longer used.

- Fixed bug in the server startup script installation

This is the first release of the nexusformat package, which is based on the NeXus Python API used within NeXpy.