Add election_status to EE data model

[jf1]

The 2017-05-04 by-election for Manchester, Gorton should be marked in EE as canceled, and EE could benefit from being able to assign this and other status values to any election. Example values below.

election_status:
Expected
Announced
Cancelled
Completed - or this could be: Polls Closed; Result Announced

If a changelog can accept a source then for the above example it would be: http://www.manchester.gov.uk/download/downloads/id/24869/notice_of_cancellation_of_manchester_gorton_parliamentary_by_election.pdf

[chris48s]

Another example of this:

Dacorum council recently scheduled an election for 1st March
https://notice-of-election.s3.amazonaws.com/local.dacorum.northchurch.by.2018-03-01/notice-of-election---borough-councillor-for-northchurch-ward.pdfsfvrsn2
and then rescheduled it for the 8th
https://notice-of-election.s3.amazonaws.com/local.dacorum.2018-03-08/notice-of-election---borough-08-03-18.pdf

a cancelled flag/status would definitely be useful

[chris48s]

also https://www.wigantoday.net/news/court-drama-as-bryn-by-election-ruled-not-lawful-and-scrapped-1-9028544

[chris48s]

https://assets.ctfassets.net/ii3xdrqc6nfw/2xxUNLHOYU0KaqiiIAeMCg/7e5e7777838ef8abf9c091144f017d5c/Notice_of_cancelled_election.pdf

[chris48s]

couple more example of this:

https://www.cherwell.gov.uk/download/downloads/id/7760/bicester-west-notice-of-countermanded-poll.pdf

http://tamworth.gov.uk/sites/default/files/councillors_docs/Notice-Of-Countermanded-Election-Glascote-Ward.pdf

[chris48s]

It would be useful to be able to link an election with a 'rescheduled' status to another record. i.e: if we set local.tamworth.glascote.2018-05-03 to postponed, we could then create a FK to local.tamworth.glascote.2018-05-25, allowing us to say something more useful in WhoCIVF/WhereDIV than "we don't know of any upcoming elections"

[chris48s]

Done in #426