SOC 2018 files in the occcodes and soccode table formats, from BLS materials

The soccode format includes educational attainment fields that come from projections data.  Projections using SOC 2018 are not available, so educational attainment comes from 2017 projections and is applied using the BLS-provided crosswalk between SOC 2010 and SOC 2018.  Where SOC 2010 occupations split, the educational attainment value is applied to all matching 2018 occupations.  Where occupations merge, the resulting occupation is left with null values.