Define basic standards of CEDA checks for NC and BADC CSV formats

[agstephens]

@wendygarland @gap736uk : Please add to the following bullets for the NC and BADC CSV data format basic checks...

NetCDF basic checks

• Conventions: should match a list of known conventions and their versions (optionally more than one convention adhered to)
• source, creator_name and institution: should be more than 3 characters?
• All variables: have long_name and units ,
• All variables: ought to have a standard_name

BADC CSV basic checks

BADC-CSV list of requirements can be read from here: https://archive.ceda.ac.uk/cgi-bin/badccsv/csvchecker

BADC-CSV minumum checks (i.e. basic level of compliance):

• first line has to be: Conventions,G,BADC-CSV, 1
• all column metadata elements have long_name attribute - this needs to have 2 elements: <desription>,<unit>
• len(list of long_names) == len(column header line when split by comma)
• has data line and last line is end data
• all lines between data and end data lines have the same number of elements as the number of long_name elements in header section