THREESCALE-8981 Remove saas mode

[eguzki]

what

Jira: https://issues.redhat.com/browse/THREESCALE-8981

• The CONFIG_SAAS env var was used to enable certain features that were only useful for 3scale SaaS. These features are no longer used and CONFIG_SAAS is not even set in 3scale SaaS deployments.
• Removed event buckets as they were SaaS only feature comment
• Remove double Gemfile management
  • Gemfile.on_prem promoted to Gemfile
  • Gemfile.on_prem.lock promoted toGemfile.lock`
• Remove env vars not used neither in on-prem nor SaaS:
  • CONFIG_CAN_CREATE_EVENT_BUCKETS
  • CONFIG_STATS_BUCKET_SIZE
  • CONFIG_KINESIS_STREAM_NAME
  • CONFIG_KINESIS_REGION
  • CONFIG_AWS_ACCESS_KEY_ID
  • CONFIG_AWS_SECRET_ACCESS_KEY
  • CONFIG_REDSHIFT_HOST
  • CONFIG_REDSHIFT_PORT
  • CONFIG_REDSHIFT_DBNAME
  • CONFIG_REDSHIFT_USER
  • CONFIG_REDSHIFT_PASSWORD

Fixes #196 Fixes https://github.com/3scale/apisonator/issues/215

TODO

• [x] changelog
• [x] clean up commits

[eguzki]

bors r+

[bors[bot]]

Build succeeded:

• ci/circleci: build