Restarting simulation from backup files

[giovannisoligo]

On Marconi and VSC-3 unable to restart from fields in modal space; simulation must be restarted from fields in physical space.
Restart from fields in modal space works from local machine (machine 0 and 1) and on Vesta.

Added a flag in compile.sh (savespectral) which has a different value depending on the machine. This flag determines whether the recovery fields are saved in modal or physical space.
flag value 1:

• local Mac
• local
• Vesta

flag value 0:

• Marconi A1
• Marconi A2
• VSC-3
• VSC-4