v5.4: release MagIC 5.4

-Support for double-diffusive convection
-Support for temperature diffusion and temperature boundary conditions in the anelastic models

v5.3: release MagIC v5.3

• Support of SHTns for the Legendre transforms: up to 60% speed-up for large
  problem sizes (Bertrand Putigny)
• Port RMS force balance analysis from MagIC 3.44 (Thomas Gastine)