modifications for the test mode

Removes comments

On 3D page, the point indicating on which chanel the user clicked on the upper spectrum is now bigger and on the graph instead of Y=0

Directory SAMP renamed as SPECTRUM. Its content was not used only for samp and images sent via samp are stored in
IMG so the name dit not really made sense anymore

Fixes error in gnomonic projection : some lines where not properly converted from python to javascript

=> emergency modifications made directly in master

Adds timer for performance testing

Adds a new down command to the yafits script

Update nodejs version from 12 (LTS, EOL was april 2022Y) to 16 (LTS, EOL is april 2024) because of a libraries update

Set iram as default LUT

Changes the way selected area is showed

Removes padding at both extremities of highcharts graph