Allow wildcards in projectile-project-root-files

So after we got haskell project identification working which is enough if the project is under version control, it would be nice if projects without vcs are recognized as well. :)

To do so, we have to allow wildcards when searching for project-root-files as well.

What do you thing about replacing `projectile-file-exits-p` with `file-expand-wildcards` again?