Commit [264c85] Maximize Restore History

Merge branch 'dev/fix-lens-distortion'

* dev/fix-lens-distortion:
explicitly instantiating lens models with float
Adding read-only and read-write coefficient accessor methods
Set has_derivative flag to true in vpgl_poly_radial_distortion constructor
set_coefficients tests for NULL pointer before dereferencing.
Unit test for vpgl_poly_radial_distortion constructor.

Matt Leotta Matt Leotta 2014-06-20