Use a standard coordinate system by default

By default, the top of the frame is at y=8.0 (see L61 in config.py). Why should this be the case? The choice of 8.0 seems arbitrary. A more standard choice would be to set the range of the vertical axis to be either (-frame_width, frame_width) or (-1.0, 1.0), but not (-8.0, 8.0).

Of course, any choice will be somewhat arbitrary, but some are more natural than others. In fact, matplotlib supports the usage of many different scales, see here.

EDIT: To be clear, there are two issues mentioned here.

1. The choice of 8.0 seems very arbitrary and (I think) should be changed. @PgBiel suggests that it could be made customizable through the config system. I agree. This is an easy PR.

2. I’d be great to support multiple coordinate systems, like matplotlib. This is a more substantial PR.

[yoshiask]

I’d like to point out that a more standard coordinate system would help devs attempting to build graphical editors for Manim (like myself), because we’d only have to scale the coordinates on objects instead of doing weird and buggy calculations to effectively move the origin.

[PgBiel]

Might be easier to have some class like

Unit(30, "px")

Also, regarding the max coords, those should probably be customizable