Blender Git Loki

Add constraints for focal length refinement

The user can apply a ranged constraint to the focal length during refinement. When the focal length is selected for refinement in the solve panel, a constraint can be applied by checking "Constrain Focal Length" and entering the appropriate minimum and maximum values. The camera focal length will only be refined within this range. This is useful when an unconstrained refinement gives an incorrect result and a suitable range is known.

This includes the following changes:
- Addition of constraint UI with corresponding RNA properties. The constraint is displayed in the same units chosen for the camera focal length. The values are restricted such that min is no greater than focal length and max is no less than it.
- Data structure modifications to allow passing of constraint values from the UI to libmv.
- Modifications to the libmv simple pipeline API to incorporate constraints.
- Constraining focal length when interfacing with Ceres (which only does unconstrained solving) through a sinusoidal mapping.

Results of tests are given at: http://wiki.blender.org/index.php/User:Sftrabbit/GSoC_2013/Documentation/Constraint_Tests