Add rake test description

No behavior change
Inflector irregular singularize rules
Adding Back Rails::Engine::Railties#engines

Removing it breaks functionality with gems such as Thinking Sphinx.
This restores it with a deprecation warning. Closes #8551
Simplify code in AS json encoder
remove 'update' duplications
update assets guide code styling

* 1.9 hash syntax
* proper formatting around one line blocks
* do-end for multiline blocks
Clarified the minute option on DateTime#change
Update guides/source/active_record_basics.md
Fix .update_all and .delete_all when using a condition on a joined table
in a default_scope.

`Model.joins(...).where(condition_on_joined_table).update_all` /
`delete_all` worked, but the same operation implemented with a
default_scope generated a SQL error because ActiveRecord ignored the
join but implemented the where condition anyways.
Update engine application layout file path
Fix typo in guides/source/engines.md
Fix typo in guides/source/engines.md
`CollectionAssociation#empty?` respects newly builded records
Fix simple expression
fix reference to ActiveSupport::ProxyObject
rake railties:install:migrations respects the order of railties
Revert benchmark helper regression. Use a #capture within a #benchmark
block. Breaks benchmark calls that return non-String values otherwise.

Revert "add benchmark helper that works in erb"

This reverts commit 904e544cc8f5846de7c31827bb5556c6a238c0de.

Conflicts:
	actionpack/lib/action_view/helpers.rb
	actionpack/lib/action_view/helpers/benchmark_helper.rb
	actionpack/test/template/benchmark_helper_test.rb
Rename :value option to :selected, in line with other select helpers
Add tests for time & datetime.
Add documentation.
Address test_create_when_database_exists_outputs_info_to_stderr failures

When tested with ruby-2.0.0-rc1 `rake test` executes this test
even if the target adapter is not mysql nor mysql2.
test for ActiveModel::Conversion#to_partial_path and namespaced models