Part 1: expose redirect URL from Apache Shiro back to React

[JasonWildMe]

This PR allows a Wildbook URL to a secured endpoint to be entered and then redireted back to after login.

For example, /appadmin/dataIntegrity.jsp is secured, and a public request to it should be redirected to /react/login/ before returning the user to /appadmin/dataIntegrity.jsp.

PR fixes #675

Changes

• Part 1: @JasonWildMe adds the "redirectURL" parameter to Login.java's returned JSON payload
• Part 2: @erinz2020 ensures /react/login/ page does not make any calls to the backend Java
  • remove call to /Collaborate if user is not yet logged in. This interferes with our ability to get the redirect URL.
  • remove call to /UserGetNotifications if user is not yet logged in. This interferes with our ability to get the redirect URL.
• Part 3: @erinz2020 If JSON payload response from Login includes a "redirectUrl" value (e.g., "/appadmin/dataIntegrity.jsp"), redirect to that URL.