BigQuery Orc & Parquet Samples

[alixhami]

This PR:

• Adds load truncate samples for Orc and Parquet file formats
• Adds load, load autodetect, and load truncate samples for JSON
• Updates Orc and Parquet samples to not specify schema. The schema is inferred for these formats, so it should not be supplied (sources: parquet schemas, orc schemas)

[alixhami]

I did not regenerate the readme because npm run generate-scaffolding did not run. I got this error:

~/nodejs-bigquery [bq-orc-samples] $ npm run generate-scaffolding
npm ERR! missing script: generate-scaffolding

npm ERR! A complete log of this run can be found in:
npm ERR!     /Users/ajhamilton/.npm/_logs/2018-09-17T22_27_15_264Z-debug.log

[tswast]

LGTM