Fix the tests (I have actually verified that these are also the 'right' fixes, rather than just making the tests pass again)

Add support for table aliasing, with a test that needs aliasing in order to work correctly. This test incidentally provides a more complicated test case (4 inner joins, 2 using polymorphism).

Integrate nested support into ThroughAssociationScope, using my concept of generating a 'chain' of reflections to be joined. It seems to work at the moment, all existing tests are passing. There may be further complications as we add more test cases for nested associations, though.

Started implementing nested :through associations by using the existing structure of ThroughAssociationScope rather than layering a module over the top

Prevent test_has_many_through_a_has_many_through_association_on_through_reflection failing for me due to ordering of the results

Signed-off-by: NSantiago Pastorino <santiago@wyeworks.com>

With config.generators becomes a way to configure generators
for current instance only. For example:

module Blog
  class Engine < Rails::Engine
    config.generators do |g|
      g.orm :active_record
    end

    config.app_generators do |g|
      g.test_framework :rspec
    end
  end
end

such definition sets :active_record as orm for engine and :rspec
as test_framework for application. The values set with app_generators
can be overwritten in application using config.generators as you would
normally do:

module MyApp
  class Application < Rails::Application
    config.generators do |g|
      g.test_framework :test_unit
    end
  end
end

Signed-off-by: NJosé Valim <jose.valim@gmail.com>

performance improvement based on discussion at http://github.com/rails/rails/commit/fbd1d306b95cc2efb6422e12d26d5818a3a42343

Credit goes to all the participants in the discussion

This reverts commit bee447a5.

This reverts commit 9eca11a4.

Signed-off-by: NSantiago Pastorino <santiago@wyeworks.com>