Update FindNetCDF.cmake with better tests

[gsjaardema]

As of NetCDF-4.5.0, the NC_MAX_VARS and NC_MAX_DIMS limits are no longer enforced, so it isn't necessary to check their values. While updating the test and whether to perform it or not, I discovered that the current parsing of NC_MAX_VARS and NC_MAX_DIMS was returning incorrect values.

To fix this, I added a REGEX to strip the C comment from the end of the string.
I also parsed more values from the netcdf_meta.h file if it exists instead of parsing some values from it and some from the nc-config script.

Tested on several versions of NetCDF and values all look reasonable