Add Scopes addon

[Kexanone]

When merged this pull request will:

• Add ability to adjust elevation and windage of optics in mrads.
• Add fitted elevation scales for PSO-1 and British Forces scopes. The default of 1.0 already works for ART II.

Implementation:

• Current approach is to apply the angle adjustments by rotating the local transform of the scope. Current center of rotation is the scope's origin, which is the easiest, but probably not the best pick.
• m_fACE_EffectiveVerticalZeroingScale attribute can be used for improving elevation accuracy, which is the slope $m$ for the fitting $y = m \cdot x$, where $x$ are tabulated elevations (from Add Ballistics addon #386) and $y$ are effective required elevations.