Preview/extended version of opa-authorizer #2

This version builds on the experimental release (version 0.1.0) and will address (without necessarily implementing everything) the following:

• Permission granularity
  • Action granularity: do we want to distinguish between e.g. Admin and Create, and between different types of writes (write vs. delete) as is done upstream?
  • look at granting permissions on the level of cell families, not just tables
  • permissions to be distinct between KeyValue and ColumnFamily
  • check permissions on each mutation
• Permission coverage
  • check ADMIN on each namespace
  • read permissions required for checkAnd* methods to prevent probing
• Logging
  • review all logging statements to reduce noise
• Other
  • investigate ways of tracking changes made to upstream interfaces
  • ensure consistency between empty implementation of interface methods (just for logging) and fallback to default impls
  • ensure that all functionality is covered by integration tests