Put property definitions in tests in separate header (tests and lecture)

Follow up from #648 (closed).

To make another step away from the problem-does-everything-mentality that was common (and a necessary evil) in dumux 2, we plan on putting the property definitions into a separate header.

Previous work accomplished in #648 (closed):

• Separate properties into properties.hh for the examples (!1933 (merged))
• Separate properties into properties.hh for the dumux-course#24 (closed)

Current goals:

• Separate properties into properties.hh for the dumux-lecture dumux-lecture#18 (closed)
• Separate properties into properties.hh for the tests

This doesn't have to be in one go. If someone edits a test anyway feel free to do this change as well.