feat(autosave): ask user if he wants to ignore changes or save it

Introduce authoring service which handles item authoring lifecycle.

SD-921 SD-657
[SD-542] Edit a Role now shows error message on attempt save a role with a duplicate name
Fix(tasks): fix assignee box UI problems

Fix assignee box overflow
Fix assignee box opening
fix(authoring): 'SendTo' > styling and code improvements

Add styling to desk selection dropdown
Fix etag problem
Improve stages fetching
Merge pull request #503 from petrjasek/feat-autosave-confirm

feat(autosave): ask user if he wants to ignore changes or save it
Merge pull request #504 from marwoodandrew/devel

[SD-542] Edit a Role now shows error message on attempt save a role with...
Merge pull request #505 from nidzix/devel

UI update