class_inheritable_accessor is removed in Rails 3.2

Use class_attribute instead

--HG--
extra : rebase_source : 92ab6f38f4f5744a335273207247c030223994a0
Load the Project model very early.

This is required to work around a circular dependency issue during class loading.
See the comment in application.rb for details.

--HG--
extra : rebase_source : 6c485dc8d9010fd05a0c6b51c785dd74e61ebbfc
Temporarily flip default Rails settings

On Rails 3.1:
<pre>
==  SetDocAndFilesNotifications: migrating ====================================
rake aborted!
An error has occurred, this and all later migrations canceled:

undefined method `update_attribute' for nil:NilClass/REDMINE/git-workdir/redmine/db/migrate/018_set_doc_and_files_notifications.rb:20:in `up'
</pre>

--HG--
extra : rebase_source : 44bc73a2829c4f4b8db2e9b44efe5d3d114152cc