Chapter 9 / 28 - privatise attributes
Merge remote-tracking branch 'arstrube/master'
tpp / 1 - add new files.
tpp / 1 - fix -Werror problems...

...this test is supposed to fail but crashes.
There is no good way to test a nullptr like this.
tpp / 2
tpp / 3
tpp / 4
tpp / 5
tpp / 6
tpp / 7
tpp / 8
tpp / 9 - this still fails.
tpp / 10
tpp / 11 - 1 of 2.
tpp / 11 - 2 of 2.
tpp / 12
tpp / 13 - crashes.
tpp / 14 - fix crash.
tpp / 15
tpp / 16