experiment with removing 'Real' from popular types

[ThierryBerger]

Embedding Real type in most popular types would allow to simplify a bit the signatures of the functions:

from:

pub fn cast_shapes(
    pos1: &Isometry<f32>,
    vel1: &Vector<f32>,
    g1: &dyn Shape,
    pos2: &Isometry<f32>,
    vel2: &Vector<f32>,
    g2: &dyn Shape,
    options: ShapeCastOptions,
) -> Result<Option<ShapeCastHit>, Unsupported>

to:

pub fn cast_shapes(
    pos1: &Isometry,
    vel1: &Vector,
    g1: &dyn Shape,
    pos2: &Isometry,
    vel2: &Vector,
    g2: &dyn Shape,
    options: ShapeCastOptions,
) -> Result<Option<ShapeCastHit>, Unsupported>