Open-sources timelines.

This represents the timelines plugin that was merged with the
OpenProject core and which had its history squashed. The timelines
plugin development was sponsored by;
Deutsche Telekom AG <opensource@telekom.de>

Requirements engineering and management were provided by;
Deutsche Telekom AG <opensource@telekom.de>
Finn GmbH <info@finn.de>

During the timelines development, the following authors have contributed
commits;
Martin Czuchra <m.czuchra@finn.de>
Nils Kenneweg <n.kenneweg@finn.de>
Romano Licker <r.licker@finn.de>
Gregor Schmidt <g.schmidt@finn.de>
Jens Ulferts <j.ulferts@finn.de>
Johannes Wollert <j.wollert@finn.de>

Quality Assurance was provided by;
Erdem Kabadayi <e.kabadayi@telekom.de>
Julia Pape <j.pape@finn.de>
Christian Rijke <c.rijke@finn.de>
Thomas Vogel <th.vogel@external.telekom.de>
Final merge with the original timelines plugin.

This includes all features that were added to timelines while
the merge with the core was being worked on.
Adds external timelines library names.

So they can be excluded when updating the copyright notice.
Updates copyright notice in timelines sources.
Merge pull request #166 from opf/feature/timelines

Open-sources timelines.