Description:
    The extension generator creates stubs for a new Mars extension.

    The generator takes an extension name as its argument.  The extension name may be
    given in CamelCase or under_score and should not be suffixed with 'Extension'.

    The generator creates an extension directory in vendor/extensions that includes
    <extension_name>_extension.rb, README and Rakefile files as well as db, lib, task,
    and test directories.

Example:
    ./script/generate extension AssetManagement

    This will create:
    vendor/extensions/asset_management/config
    vendor/extensions/asset_management/config/locales
    vendor/extensions/asset_management/app/controllers
    vendor/extensions/asset_management/app/helpers
    vendor/extensions/asset_management/app/models
    vendor/extensions/asset_management/app/views
    vendor/extensions/asset_management/db/migrate
    vendor/extensions/asset_management/lib/tasks
    vendor/extensions/asset_management/README
    vendor/extensions/asset_management/asset_management_extension.rb
    vendor/extensions/asset_management/lib/tasks/asset_management_extension_tasks.rake
    vendor/extensions/asset_management/config/routes.rb
    vendor/extensions/asset_management/config/locales/ja.yml
    vendor/extensions/asset_management/test/fixtures
    vendor/extensions/asset_management/test/functional
    vendor/extensions/asset_management/test/unit
    vendor/extensions/asset_management/Rakefile
    vendor/extensions/asset_management/test/test_helper.rb
    vendor/extensions/asset_management/test/functional/asset_management_extension_test.rb
