GUI-274: Heads up!  Don't allow redirect_url to be set in a hidden param.  Prevents arbitrary redirects when deleting a snapshot on the volume-snapshots page.
GUI-274: Leverage new sanitize_url method to prevent arbitrary redirects in login and change password forms
GUI-274: Add unit tests for sanitize_url method
Merge pull request #419 from eucalyptus/GUI-274

GUI-274: Prevent arbitrary redirects in login handler via sanitize_url method