v2.0.0b1

• Adds validation module to check the contents of base classes and validate against application definitions.
• All base class and application definition files are now included in the package, although the path to the definitions directory can be redefined either using nxsetconfig or setting the NX_DEFINITIONS environment variable.
• Adds three new NXgroup methods, check, validate, and inspect, which produce colorized output.
  • The check function compares the contents of a group and its children to their base class definitions.
  • The validate function validates the contents of a NXentry group against an application definition.
  • The inspect function produces a formatted version of the base class XML file.
• Adds a command-line script nxcheck to check or validate a NeXus file.
• Adds a command-line script nxinspect to display a base class definition.
• Changes the NXfield statistical methods to match the equivalent NumPy methods. For the old behavior, the NXfield should be wrapped in a NXdata group without specifying axes.
• Updates requirement to use Python v3.9, now that v3.8 has reached its end-of-life phase.