stereo: Use std::equal instead of IsEqualElements

Code reuse for the win! Hooray less code!
ip: Have interest points always written in order of tiles

This means we should always produce the the IPList in the same order
no matter how many cores that have or what order the threads decide to
operate.

Sorting before matching or RANSAC is no longer required.
CameraBBox: Fix bug
CameraBBox: Use initial guess if available
CameraBBbox: Improve the search for initial guess

Also introduce the variable cambbox_mode. When computing the DEM camera bbox
we prefer to preserve established behavior.