Allow separate OpenGLContexts for multiple windows

[adamski]

I'm using this project and module as a testbed for a multi-window app I am working on. For this use-case, I need both a SharedOpenGLContext for the main app window, and extra contexts for each "satellite" window.

It looks like a bit of refactoring would be needed to turn the SharedOpenGLContext into a wrapper that can have multiple instances. I would propose:

• Move SharedOpenGLContext to e.g. OpenGLWrapper.
• Refactor Plot2D to accept a reference to an OpenGLWrapper
• Use e.g. SharedResourcePointer to make OpenGLWrapper a singleton (for the main window)

Is this something you'd be interested in merging?

[JanosGit]

Nice to hear that this module is useful four you! Your ideas sound sensible to me, so feel free to send a pull request.

I'm currently working on a project with a tight deadline that uses this repo with some not yet made public additions, so I'm not sure how much spare time there is for me to merge a pull request soon before the work on that project has been finished (the same goes for tracking down the Windows-related bug reported in #3), however I'll do my best!