Add responsible Server Side Filter.
Introduces status filters in timeline UI.
paginate statuses in api/v2.
Removes client-side filter for responsibles.
Improves cuke to run faster.

The new timeline will render much faster, additionally, the scenario
name was fixed from the previous copy/paste duplucation.
status display. server side filter.
Merge branch 'feature/server-side-filters' of github.com:opf/openproject into feature/server-side-filters
no none elements no more.

for types.
-1 filters for null values.
Adds cukes for responsible filter.
Changelog.
refactoring. pes w/ no responsible test added.
Merge branch 'feature/server-side-filters' of github.com:opf/openproject into feature/server-side-filters
Merge pull request #465 from opf/feature/server-side-filters

Feature/server side filters
runs on my machine, travis likes it, good to go.