Rename Base.constrain to Base.with_scope so it doesn't conflict with existing concept of database constraints.  Make scoping more robust: uniform method => parameters, validated method names and supported finder parameters, raise exception on nested scopes.


git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@2888 5ecf4fe2-1ee6-0310-87b1-e25e094e27de