YAML -> netCDF converter

[RobertPincus]

YAML is not a convenient file format in all contexts. Users have expressed interest in a tool that converts YAML flight phase files to netCDF time series files. Roughly the idea would be to copy the time variable from some reference file, than create an array with dimensions (time, segment_kinds) with True/False values for each segment kind defined in the file. @d70-t points out CF conventions can be used to map arbitrary segment names to segment_kinds.