The Jackett widget was using the api key in api requests however this
is not necessary as the endpoint we use doesn't require it. If Jackett
authentication is enabled then the password field should be used
instead.
Fixes the error that occurs as seen in (#437, #1799 and #2794) which
occurs due to the way password authentication works in Jackett. We now
make a login request to Jackett to get the cookie and then use that
cookie to make the actual request to the Jackett API.
