Addition/fix of documentation

[cecilehannay]

Request:

• why is the frequency of output for each component have a different entry datatype, e.g. POP, CICE and CAM have different dtypes
• in the namelist time tutorial, why is POP the only one with the arguments units of time as output and not the CAM or CICE or others? Is there a default?
• Also the link in the POP namelist does not work, asks for login
• Can we have namelist exercises for land, ocean and sea ice?