Escape characters should not be in object names.

Original pull request: https://github.com/cloudfoundry/cloud_controller_ng/pull/118.

Adjusted the regular expression to account for Unicode characters. I did not explicitly blacklist a list of escape characters as suggested by @calebamiles. I feel as though there will be to much of a chance that we would forget to blacklist a specific case and it is therefore safer to simply white list a larger pool of allowed characters.