[WIP] Bugfix/contact account company

fixed bugs in API of contact and accounts:
https://github.com/sulu-cmf/SuluContactBundle/issues/46
https://github.com/sulu-cmf/SuluContactBundle/issues/26

close after merge

- [ ] test coverage
- [ ] finish the code
- [ ] gather feedback for my changes
- [ ] submit changes to the documentation

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| Tests pass?   | yes
| Fixed tickets | yes
| Doc           | non