NCAS RADAR v1

[joshua-hampton]

Start of adding checks for the NCAS-RADAR standard. This standard is in some ways more relaxed than NCAS-GENERAL and NCAS-IMAGE. For example, there are a large number of variables permitted by CfRadial (and therefore NCAS-RADAR), but it is not expected that all of them would appear in one file. There are also looser restrictions around variable attributes, for example, the type of each variable is not defined, but stated to be "one of byte, short, integer, float, double", and _FillValue is "of the same type as the data variable".

What needs to be done:

• spec file(s) that contain this information. A couple of ways to do this, either one spec file per variable, and checksit only uses ones related to variables in the file, or one spec file with all variables in, and rather than returning warnings or errors when variables aren't found in the file checksit ignores them because it knows its an NCAS-RADAR file (I think this second option would need some sort of attribute/variable carried through within checksit that states this file is NCAS-RADAR, the first option would require logic similar to that used for NCAS-GENERAL that identifies which specs are needed).
• rule_attr paramter added to checksit.generic.check_var, to allow some variable attributes (e.g. type) to be checked against a rule
• a new rule same-type-as, which takes one paramter which should be the name of a variable, and checks the value of the attribute (e.g. _FillValue) matches the type of the stated variable

I'm sure I'll find more as I go.

[joshua-hampton]

PR #48 address the needs of NCAS-Radar checks

[joshua-hampton]

PR merged, closing this issue.