changed code so that we can concatenate one or more ref_points files to ref_points.local.php

bugfixed inverted lon/lat parameters on RefPoint (+ added convenience ref_point->get_name())

Refacto of Tiles handling and simplified a bit file naming for tiles/params.
By the way, fixes #297

THIS COMMIT BREAKS FILE LAYOUT AND REQUIRES MIGRATION (SEE BELLOW).

To migrate data :

cd tiles
find . '*.jpg' -exec rename 's/[^\/]*_(([0-9]{3}_){2}([0-9]{3}))/$1/' {} \;...

do not display ref_points and panorama further than 25km from the current one (tunable in constant)

Use propper RefPoint::get_all() instead of requiring ref_points.local.php

moved the ref_points path to a constant.

some request input checking/sanitization

The one-step upload now handles as well the tiles generation and stops on generation errors if needed

fixes bug : image_loop not returned properly after being parsed from file

tolerate that the dir exists before tiles creation