Added Anti-Aliasing to the Render Settings

[CrushedPixel]

Added an Anti-Aliasing option to the Render Settings (disabled by default, up to 8x).
When enabled, the video is rendered at a higher resolution and scaled down using ffmpeg to provide smoother edges.

How it looks in the render menu:

Here's a frame, rendered at 1080p, without anti-aliasing:

Here's the same frame with 4x anti-aliasing: