Change asserts() to soft-asserts in Vcs-Cache.

- Prevent crash when creating a project.
- Use QDir to normalize the path (as it is constrcuted in
  the assert anyway).
- Print proper warnings.

Change-Id: Ib6fa3c564aff20b73d6efc08ca3a13688fd97dce
Reviewed-by: hjk <qthjk@ovi.com>