Move the Place comparator to an init file to have .comparing and not .comparing.comparing

doc/build/doctrees/analysing.doctree

doc/build/doctrees/comparing.doctree

doc/build/doctrees/computing.doctree

doc/build/doctrees/database.doctree

doc/build/doctrees/environment.pickle

doc/build/doctrees/gettingstarted.doctree

doc/build/doctrees/index.doctree

doc/build/doctrees/moving.doctree

doc/build/doctrees/processing.doctree

doc/build/doctrees/rendering.doctree

doc/build/html/_images/apcv.png

doc/build/html/_images/contrast_weighted_nearness.png

doc/build/html/_images/load_image_posorient.png

doc/build/html/_images/load_image_rowid.png

doc/build/html/_images/michelson_contrast.png

doc/build/html/_images/scene.png

doc/build/html/_images/skyline.png

doc/build/html/database.html

...uild/html/example/database/load_image_posorient.hires.png

doc/build/html/example/database/load_image_posorient.pdf