Expose certain PP5 context properties in PP5EnrollTransform

@JordanCheney @mmtaborsky While the default PP5 settings are good for getting the maximum recognition performance under all conditions, they are non-ideal when enrollment speed is a concern. This PR allows certain context properties to be set in the algorithm string that are particularly relevant for changing the speed/accuracy tradeoff.
One other option is to have this be the total pixel measure (say 40) and call ppr_get_size_from_pixels() internally to convert this to the proper value so the user doesn't need to worry about it. At some point we may also want to normalize whether the minimum size of a detector refers to IPD or total bounding box width across OpenBR but that can be implemented later.