rotomap.moles.load_image_moles: tolerate non-ints
rotomap.moles.load_image_moles: tolerate non-ints

Make loading more robust by tolerating non-integer values for
co-ordinates, as long as they convert to ints.

Test Plan:
$ ./meta/run_tests.sh
.. Run 'rotomap-edit' on a map with float co-ords ..

aevri/mel,aevri/mel