Upgrade from Tycho 2.3 to 2.5
See also:
- https://github.com/eclipse/tycho/blob/master/RELEASE_NOTES.md#240 (2.4)
- https://github.com/eclipse/tycho/blob/master/RELEASE_NOTES.md#250 (2.5)
- https://www.eclipse.org/lists/tycho-user/msg09145.html (more information on changes in 2.4 regarding combining test and non-test code in a single plug-in)