Rename to avoid stutter

[umeat]

rinex.RinexFile, rinex.ParseRinexFile - Should these be rinex.File and rinex.Parse (or ParseFile)? Does "RinexFile" have to be an actual file or is it just the header plus a collection of obs (if it's always in memory and never written to/from a file)? In either case should the type still be called "File"?

Also scanner.Scanner - not sure we need this package / type. Definitely want a reader to so we don't have to parse an entire file into memory, and needed the line number for scanner.

[umeat]

ParseRinexFile should probably be rinex.NewFile(io.Reader) rinex.File.