Conditionally disable RenderManager

"RenderManager" is conditionally disabled by preprocessor "ENABLE_DYNAMO_SCHEDULER". This pull request has got not real code changes, it is only meant to reduce the final PR for folding visualization into scheduler.

Hi @aparajit-pratap, please have a look at this one. Thanks!
I don't think we'll be needing the ```RenderManagerOnRenderComplete``` event handler either post scheduler.