Improve and promote the alerts service

[RichardTaylor]

Particularly given the majority of users are reading the site rather than making requests there should perhaps be more help for those using the service as a reader / someone wanting to be alerted to information that interests them.

• Currently for whatever reasons too many people sign up for alerts for all requests marked successful / partially successful (Deter accidental subscription to alerts for all successful requests #4884)
• Advice on setting up alerts is currently in a blog post https://www.mysociety.org/2014/09/29/subscribe-to-foi-requests-on-any-topic/ and not integrated into the site.
• The "journalist?" link in the footer is a link to the Pro service. The ability to sign up for alerts should be mentioned under the "Plus, all the power of WhatDoTheyKnow" heading on that page at least.
• Is the function of the "follow" button obvious?
• Consider how a local journalist might actually want to use the site eg. to sign up to all responses from public bodies in their area - or even better relating to their area. (Would need geographic tagging of bodies (geotagging of authorities #77) and threads/requests/responses)
• Mention alerts on the advances search page - it's not just advanced search - but advanced alert setup https://www.whatdotheyknow.com/advancedsearch

[garethrees]

Duplicate of #2735