Force title property for templates

__Tasks:__

- [ ] test coverage
- [ ] gather feedback for my changes
- [ ] submit changes to the documentation

__Informations:__

| Q             | A
| ------------- | ---
| Tests pass?   | yes
| Fixed tickets | none
| BC Breaks     | Every template definition must now contain a property named `title`, therefore the tag `sulu.node.name` is not necessary anymore
| Doc           | TODO
Will we really do this? I think that it is better, but didn't we say it is a too big break in BC? Haven't we discussed that in an issue?