[webui] Don't fail if no HTTP referrer was provided on login

Otherwise the app crashes when no referrer was provided. This can harm
us especially users forbid their browsers to set that header field.

[dist] Add missing release notes entry for bcrypt

This adds a release notes entry regarding the bcrypt implementation from
PR #3814

Commit: d0fd0bdb

[api] Drop unused Buildresult::index2code

Move to blowfish hashing algorithm

[api][webui] Include again direct_http

[webui] Fix typo in error message

Because obs_factory still using direct_http method.

The old test cases needed some adaptions in order to work properly
again.

This includes:

- Move to blowfish passwords in fixtures
- Drop tests or expectations which are no longer valid

- Fixed a typo
- Rephrased it

Blowfish (which is used by bcrypt) is by far more secure than md5.
Old passwords will be re-hashed after a successful login.

Validations were dropped because they should not be tested. It just
makes testing harder (overtesting).

[dist] Use the codecov image for master

[dist] Require group www

We use it in a scriptlet and it's not provided by
default anymore on openSUSE.

[api] avoid multiple hits of same package on maintenance branch

happens when you get the same package instance via multiple OBS:Maintained
entry points via project linking

The target_package strings takes also the possible different link_target_project into account.

Refactor backend calls to Backend::Api (part 7)

Update acts_as_tree to version 2.7.0

Fix error when trying to require the dependency automatically

No need to have this method is now unused

For that source_file, write_source_file, meta_from_project and
meta_from_package methods were created in Backend::Api

Move rebuild command to the Backend::Api

Instead of requiring each file one by one we can do it automatically

Instead of ActiveXML.backend.direct_http

Move backend calls to Backend::Api and refactor the method to not
calculate the path

Refactored to use file_list method of Backend::Api

created a worker_status method in Backend::Api for it

Created a build_dependency_info method in Backend::Api to the call
instead of using ActiveXML.backend.direct_http

Re-use build_results method

Moved the method there and refactor to use Backend::Connection instead
of ActiveXML

Instead of using a direct call through ActiveXML we are re-using
the file_list method of Backend::Api

Move backend test tasks mixin to be part of the Backend::* lib

[webui] Fix overlay in Kiwi Editor