Feature/123 rules for cloudtrail codestart and rds

[phelewski]

Partial for #123

This covers the CloudTrail, CodePipeline, & RDS rules for Terraform11.

• Changed severity for the following rules:
  • CLOUDTRAIL_ENCRYPTION
  • CODEPIPELINE_ENCRYPTION
• Added codepipeline tag to CodePipeline rule
• Split the DB_INSTANCE_ENCRYPTION rule into 2 rules
  • DB_INSTANCE_ENCRYPTION now checks to ensure that storage_encrypted is set to True IF replicate_source_db is not present
  • REPLICA_DB_INSTANCE_ENCRYPTION (new rule) checks to ensure that kms_key_id is provided if replicate_source_db is used
• Adjusted the assertion for the RDS_CLUSTER_ENCYPTION rule as encryption is enabled by default in some scenarios
• Added RDS_PUBLIC_AVAILABILITY to testtf function call