move r12689 awesome_nested_set modification to config/initializers/10-patches.rb (#7920)

git-svn-id: http://svn.redmine.org/redmine/trunk@12733 e93f8b46-1217-0410-a6f0-8f06a7374b81
Gemfile: use awesome_nested_set 2.1.6 gem

git-svn-id: http://svn.redmine.org/redmine/trunk@12734 e93f8b46-1217-0410-a6f0-8f06a7374b81