Develop debug mask

Sorted out the problem: not creating symbolic links with the masks, because they already existed, however the mask could have changed along the time and the symbolic link must be remade to a new file. The solution --> Now it copies the mask and overwrites it if it already exists.

@pabretonniere @eexarchou

See merge request !15

Changed the way of copying mask.regions, if it exists it doesn't copy anything. I noticed when introducing other changes

"Needed the changes for overwriting the masks everytime I run setup.development"