upgrade map plot gridded (lat/lon) netCDF data (psyplot)

[annefou]

• migrate to psyplot 1.2.1

• Add a field to allow users to specify the title for their plot

• When netCDF file contains more than one field, it plots the first one only.

  • Add an option to select one index when the file contains more than one field (could also be via a variable value such as time/year, etc.)
  • Add an option to have multiple plots on the same plot.