Cosmetics modifications on graph appearanceO

FITS toplevel dir is now found in env var YAFITS_FITSDIR and is capable of processing symbolic links to directories

Added context informations to the informations exported by copy to clip board( verbatim or json ). These are the file name and the slice index when the cube is 3D

Now modals containing measurements results have a copy and copy as json buttons to store the contents of the modals in the clipboard