Add a 50 px wide line/box to live view

[Tuskiurhil]

Dahua's IVS Rules require that targets be at least 50px wide to make sure that they're properly recognized by their AI. (e.g. [S]mart [M]otion [D]etection)

Implementing the ability to have a line and/or box on the live-view that has a width of 50pixels will make it easier to ensure proper installation of the camera.