Add procedures concept mapping

[a-chahin]

This pull request adds two mapping tables for procedures. The first CSV file proc_itemid contains itemid to omop_concept_id and omop_concept_code for SNOMED. The second CSV file proc_datetimeevents is for datetimeevents. The concepts are also mapped to omop_concept_id and omop_concept_code for either LOINC or SNOMED. Mapping codes were reviewed and verified by @xborrat.