move utility function from NetcdfDataset to Misc
WIP: Significant refactoring of sigmet reader.

Still working towards having better shaped vars. Significant movement of
code out of IOSP into volume scan class, since that was the only user.
Also moved a lot of date parsing to subroutines and use of CalendarDate.
WIP: More refactor of Sigmet IOSP.
WIP: Start trying to directly place rays.
WIP: Can open file, but still need to actually get data to vars.
WIP: Set variable specific object.