OpenTK.Toolkit will now initialize OpenTK.Configuration and
OpenTK.Platform.Factory explicitly. It can also receive an optional
ToolkitOptions parameter to influence the OpenTK.Platform implementation
that will be chosen. Finally, it explicitly implements IDisposable to
clean up after itself.
Added IDisposable interface to all classes holding native data that must be freed. OpenTK.Toolkit.Init() now returns an IDisposable instance that can be used to cleanup all native data held by OpenTK. This is useful when re-initializing OpenTK (possibly in a new AppDomain), as is the case in the Example browser.
