Adds checkers to support the [NCEI NetCDF templates v2.0](https://www.nodc.noaa.gov/data/formats/netcdf/v2.0/) for the following feature types:
- point
- timeSeries
- trajectory
- profile
- timeSeriesProfile
- trajectoryProfile
- grid
Updates the global sea_name attribute check to query the NCEI vocabulary lookup service
Drops check for allowable variable names for elevation variable
Drops requirement for a comment attribute
Support for swath feature types will be added once NCEI guidance is in place.