add safe_image_zoom
integrated the interactive ROI selection in the main script
impose extension to all the tmpfiles to save memory
abort pipeline execution if no sift matches
fix bug related to ROI coordinates query from the main script
add zoom_2d: safe zoom without alias, and safe against inf/nan

add zoom_2d: safe zoom without alias, and safe against inf/nan

incorporate zoom_2d
add an optional parameter to homography_cropper indicating a subsampling
factor f to be applied to the output image. Thus the final homography will
be Z*H, where Z=diag(1/f,1/f,1)

added global_params still not zooming
add global parameter subsample_factor to rectify_pair:
if the factor z > 1 then the rectified images will be subsampled by a factor z
Merge branch 'master' of github.com:gfacciol/s2p

Conflicts:
	python/common.py
Merge branch 'master' of https://github.com/carlodef/s2p
Merge branch 'master' of github:gfacciol/s2p

Conflicts:
	main_script_pairs.py