Replace DisabledByDefault with disabling each cop

[shima-zu]

Summary

When DisabledByDefault is true, all cops are disabled in the default configuration. This means that all extension cops are disabled by default as well.

The extensions are outside the scope of omakase, and user may not realize that it has been disabled.

Workaround

The following is workaround, but I don't want to write them in my configuration.

inherit_gem:
  rubocop-rails-omakase: rubocop.yml

inherit_from:
  - .rubocop_todo.yml

require:
  - rubocop-rspec
  - rubocop-rspec_rails

RSpec:
  Enabled: true
...

RSpecRails:
  Enabled: true
...

[koic]

IMHO, this seems like a reasonable change in the sense that it only affects the minimal set of cops targeted by rubocop-rails-omakase. From the perspective of dependencies, how 3rd-party cops that are not detected by rubocop-rails-omakase behave can reasonably be considered outside the scope of its influence.

It also appears to provide a solution to the issue raised in #14. While listing departments may introduce some redundancy, to my knowledge, there is currently no better method for specifying them.

[koic]

As with cop names, these department names should also be listed in ASCII order.

[shima-zu]

Fixed 5a5b628

[koic]

I'm not sure if this proposal will be accepted, but for now, squashing the commits into one would be appropriate.