Bring back "database already exists" messages when running rake tasks

When running tasks such "rake db:setup", instead of showing messages
like "db_development already exists", it was showing a big stack trace
and a message "Couldn't create database for ..." with the configuration
options, a very confusing message with a big trace.

This brings back the functionality present in 3-2, showing the same
message.
Deprecate `Rails::Generators::ActiveModel#update_attributes`

Deprecate #update_attributes in favor of `#update`.

ORMs that implement `Generators::ActiveModel#update_attributes` should change
to `#update`. Scaffold controller generators should change calls like:

    @orm_instance.update_attributes(...)

to:

    @orm_instance.update(...)

This goes along with the addition of `ActiveRecord::Base#update`,
introduced in cb2bd4aa619d9329c42aaf6d9f8eacc616ce53f4.
Fix AR tests due to Mysql constant not being defined
Collection radio buttons and collection check boxes through FormBuilder render
the provided block.

In the case of having a form_for method being called, the block for each
collection would not be passed and thus the result expected was always the same.
This patch passes the block to the original method like it would be assumed.
Adding tests for ActiveModel::Model

* Verifying persisted? is false when Model initialized
* Passing nil to Model should not blow up
* Changing test name to the one suggested in pull request comment
Associaton -> Association
Remove WIP from Working With JavaScript Guide.

Now that we've fixed the fibs example, this is good to go.
Allow value to be set on date_select
Merge pull request #8925 from colinbm/date_select_value

Allow to override the value on date_select
Merge pull request #8917 from adomokos/adding_more_tests_to_activemodel_model

Adding tests for ActiveModel::Model
Add regression test to #8907
Merge pull request #8916 from josemota/collection-with-block

Collection radio buttons and collection check boxes through FormBuilder render the provided block.

Closes #8897
Test to allow Range including DateTime and DateTime::Infinity

Closes #8587
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