Another pass at fixing stereo deps.
StereoSettings: Provide defaults for all of them
dg_mosaic: Fix microsecond formatting and xml parsing bugs
Enable sparse_disp for all ASP alignment methods
dg_mosaic: Fix artifact with a gap showing at stitch boundary
dg_mosaic: Set or wipe image tags rather than keep them wrong
dg_mosaic: Compute the new camera corners
sparse_disp: Finish merging Bens sparse_disp