Create radian and degree conversion functions

Many models make use of things like

```c++
static const double rad_per_degree = M_PI / 180.0;
```

We should provide this as a constant in the Math Utils model. Or (maybe better), we can mimic Python's `math.radians()` and `math.degrees()` functions.

```c++
// Maybe provide both?
inline constexpr double DEG_TO_RAD =  M_PI / 180.0;
double some_value_in_radians = MathUtils::radians(10.0);
```