Removes timelines_steps in favor of timelines_then_steps.

This also fixes most argument ambiguities in timelines_then_steps.
Adds step for timeline configuration of types.

Timelines now can be configured to show a certain type only via
filtering.
Fixes some cukes.

Planning elements and issues are merged into work packages, steps now
also reflect this. Also fixes some whitespace.
Adds cukes for serverside timeline filters.