Robustly parse strings that represent NaN and Infinity

[cwardgar]

From the mailing list:

In NetCDF-Java and THREDDS, we currently use Double.valueOf (or similar) to parse strings as floats. As the Javadoc states, only the literal string "NaN" is interpreted as Not-a-Number and only the literal string "Infinity" is interpreted as infinity. We ought to be more lenient. At the least, do case-insensitive matching and accept the "inf" string.

[DennisHeimbigner]

Agreed, although finding all the relevant places may be a bit of a chore.