Update database.yml when rails new <new_app> -d oracle specified

[yahonda]

Summary

This pull requests updates database.yml for Oracle enhanced adapter users.

• Install "activerecord-oracle_enhanced-adapter".
  Oracle adapter used to be a bundled one. Now it is a 3rd party one.
  Also "ruby-oci8" is a required gem for CRuby, not for JRuby.

• Remove oracle entry for JRuby since Oracle enhanced adapter
  supports both CRuby and JRuby with a single gem.

• Change adapter name from oracle to oracle_enhanced in the oracle.yml.
  Not changing -d oracle

• Update DATABASE_URL entry to use a dash instead of an underscore
  Refer d72a0cb for the reason.

[tenderlove]

LGTM

[pixeltrix]

@yahonda just out of interest, do you know where the latest version of the non-enhanced code is meant to be? We have a bunch of conditions in our test suite for :OracleAdapter and I'm wondering how relevant they still are.

[yahonda]

Oracle enhanced adapter is a fork version of original Oracle adapter (OracleAdapter).
The original OracleAdapter has not been maintained anymore since at least when I started maintaining Oracle enhanced adapter in 2011.

Oracle enhanced adapter emulates OracleAdapter by setting emulate_oracle_adapter: true .
https://github.com/rsim/oracle-enhanced/blob/master/lib/active_record/connection_adapters/oracle_enhanced_adapter.rb#L84-L89

emulate_oracle_adapter: true is set by default at ActiveRecord unit test connection configuration.
https://github.com/rails/rails/blob/master/activerecord/test/config.example.yml#L69

Then :OracleAdapter works.

[pixeltrix]

@yahonda thanks for the clarification 👍