Create sanitized, GDPR-compliant database dumps

[balintbrews]

(Extracted from #8.)

• Refactor the dump task to allow both a normal dump and a sanitized dump.
• Augment normal drush sql-dump commands with machbarmacher/gdpr-dump to perform sanitization on the fly.
• Upload sanitized GDPR-compliant database dumps to s3.

We'll need the ability to specify the gdpr-replacements parameter that denote which db tables and columns to sanitize to be stored in .spark.yml, but then converted to the required JSON format in the Spark command task so it can be passed to the gdpr-dump command.

gdpr-replacements: 
  - tableName
      columnName1:  
        formatter: formatterType
        ... 
      columnName1:  
        formatter: formatterType
        ... 

[balintbrews]

Closing this in favor of #30 and other issues which will provide the desired functionality.