making redirection on login configurable

In few sites it was required to set custom redirection link after login. By default view method decorator redirects always to the original location. Right now is possible to define which views should be redirected after login to the specific location. This is particular useful if you want users to see all data from specific group without going to the drop down menu.

```
bin/omero config set omero.web.login_redirect '{"redirect": ["webindex"], "viewname": "load_template", "args":["userdata"], "query_string": "experimenter=-1"}'
```

redirect - list of view names or urls should be redirected after login
viewname - a name of the view used in urls.py
args - arguments associated with a view
query_string - part of URL that contains data to be passed to web applications such as CGI programs.