added documentation for the new request_stack service
Merge pull request #2956 from fabpot/request-stack

added documentation for the new request_stack service
[#2956] A few more changes to the scopes chapter to update the new way of working with the request service
[#2927] Fix thanks to @xabbuh
remove double backtick of class directive
add missing backslash
[#2927] Adding missing word thanks to @xabbuh
Merge branch '2.2' into 2.3

Conflicts:
	cookbook/form/dynamic_form_modification.rst
Merge branch '2.3'