Added Spark PCA result wrangling commands
Correction to dataset size.

The BigQuery table is 3.34TB uncompressed but the actual uncompressed files on Google Cloud Storage are smaller.

gsutil du -sh gs://genomics-public-data/1000-genomes/vcf
1.12 TB     gs://genomics-public-data/1000-genomes/vcf
Merge branch 'master' into qc-codelab
Updated singleton QC check.

* added all-positions VCF created by @gregmcinnes
* added singleton result from vcftools
* fixed a bug in the singleton query
Merge branch 'qc-codelab' of github.com:deflaux/codelabs into qc-codelab