Font size should be independent of zoom

[MattFerraro]

Currently, if you zoom in and out the font size for the plane labels "Front", "Top", and "Right" all get bigger or smaller. Zooming in or out makes the labels illegible.

A more aesthetically pleasing effect would be if the text labels stayed one size no matter the zoom level, so they are always legible.

One edge case this creates is what to do when you zoom out so much that the labels are bigger than the planes. It's okay to ignore that case for now.