Added support for normal and index arrays.
Added seperate callback function for toggle button.

* Button objects are now passed to callback functions.
Added program arguments.

* The init() function can now take optional command-line arguments.

* The --disable-mods option has been removed. This functionality will
  eventually be provided by vrui-launcher.
Restructured directory.

* Rendering classes and functions moved to separate files.

* Created 'core' and 'utils' directories.
Moved submodule imports to main __init__.py

* Submodule imports have been consolidated. The vroom API is now defined
  in vroom/__init__.py.

* The get_resource() function and related classes have been moved to
  utils/resources.py.

* The random_{vertex}{color} functions and generators have been moved
  utils/generators.py
Added resources and generators utility files.

* resources.py contains the get_resource() function and related classes
  that were previously in vroom/__init__.py.

* generators.py contains the random_{vertex}{color} functions and
  generators that were previously in vroom/__init__.py
Added internal documentation to code.

* Code comments have been added with examples.

* __all__ variable has been added to avoid collisions with color names.
{re}load_module functions rewritten.

* Common code for {re}load_module functions moved to _get_module().

* Import now done via load_source() so applications can have a non .py
  extension (.vroom maybe).
Drawing primitives moved to separate files.
GLArray class renamed to Buffer.
Updated to use Buffer instead of GLArray.
Added documentation to code.
Updated to use Buffer instead of GLArray.
Added center() function which computes the center of an array of points.
Moved global variables and aliases to core/environment.py.
Moved color definitions (red, green, blue, etc.) to core/color.py.
Added documentation to code.
Added datatypes file with BooleanOption class.

* The BooleanOption class is useful for defining variables for binary
  states (like lighting) which will be toggled on/off.
Added data_stream file with classes for inter-application communication.
Updated application class and interpreter to handle communicate() callback.