Rotest

- fixed statistic UT failure - replaced queue with manager.queue
- added core log as artifact of failed builds
- minor doc fixes

docs and builds fixes

* Tutorial doc fixes
* Added default DJANGO_SETTINGS_MODULE and a warning when using it
* Fixed current block pointer after finishing a flow

* Changed some log messages in store_state
* Updated docs around using resources and complex resource and added image

* global rotest settings can now be declared in the django settings module (deprecating rotest.yml)
* the field django_settings in the rotest.yml is no longer supported (so make sure to always declare the env-var)

* Requesting resources gives a more informative error message (no such resource/resource taken/no user/other)
* Register_resource_to_admin(model) can now take no argument and figure by itself all the fields and links