1. Write new lexical structure section.
2. Resolve DRILL 1920 (remove mention of bytea in 003-functions.md), other occurrences already removed.
2. Use table/column alias terms consistently, alias preferred over qualifier per Andries.
3. Make miscellaneous JSON ref clarifications.
4. Shorten/simplify Parquet ref example by using the default dfs.tmp workspace and removing unnecessary back ticks.