phpdoc fix
Made REST output indenting optional
Add tracking of the prepended config file

This allows the container to know that the file is involved in the config and so should be tracked for changes to reload the cache in debug mode.
Courtesy to @lolautruche who just listed it as an inconvenient of prependExtensionConfig during his SymfonyLive talk
impl/EZP-22163 Implemented user/sessions/<id>/refresh
plus refactoring of user/sessions. Specifications have also been updated
Add bc doc on RESTv2 POST /user/sessions changes
(cherry picked from commit eb842709ebe1dd99d48084d7395d9a42ac511b1d)
Fixed missing ";" in EzPublishRestExtension

See #791
Also added file_get_contents() to YAML to be compliant to Symfony 3.0
EZP-22617: Implement ISBN FieldType
Added tests 
My Integration Test denotes some issues, I was not able to find out where to fix / setup the field settings properly.
Help, please?
Included $message param reference in comment 
Removed leftovers from developing tests
Added two missing methods. (Thank you, Travis)
Defined auxiliary validation methods as private 
Fixed PHPDoc
CS. Moved const definitions to the proper place
Note to self: Copy + Paste requires actual reading of the result. :(
Rendering still mapped null field type
Fixed comment to reflect this field type's context (again, copy and paste without proper reading. A thousand apologies)
CS
CS (ty, robot)
Fixed for unit tests
Attempting to fix validator errors
Missing include