User suggestion: add support for displaying angles [0°, 360°)

[arouinfar]

A user wrote into phethelp:

Vector addition PHET shows negative angles rather than positive angles in quadrants 3 and 4 of Cartesian plane when the “show theta” button is pressed. It would be better for student understanding if the angle (counterclockwise from East) could take any value from 0 to 359 degrees.

Currently, the angle ranges (-180°, 180°] which is an appropriate choice. However, always defining the angle counterclockwise from the positive x-axis could be preferable for some users.

I would consider adding support displaying the angle as [0°, 360°) via query parameter, but we can defer further discussion until this sim is revisited.