Add diagnostics

[ddeepwell]

Include more diagnostics:

• Max and min of:
  • vorticity components
  • density always
  • salt/temp
• Max of:
  • (local) enstrophy-dissipation ratio (rather than global which smooths things too much)
• Richardson number
• Standard deviation of any field
• Energy flux through planes

Try to give max and min of all interesting variables. This gives localized quantities. Global quantities should also be found.