Edit and cancel requests, with audit logs

[timalces]

Aims to resolve #12, #20 and #21.

Editing and Cancelling Requests

• Change Requests that still have future actions to carry out can now be cancelled. If cancelled no future actions will be taken for that request
• Change Requests taking place in more than the next 5 minutes can now be edited
• Change Requests are edited using the same wizard as when creating an event
• This includes calculating new costs forecasts based on the request's newly chosen attributes

Manage Events:

Edit page:

• If a request is cancelled, it is removed from the manage events page
• If a request is updated, its new attributes are reflected in the manage events page
• Slack messages are sent when a request is updated or cancelled

• Adds a new ChangeRequestAuditLog model, with a log created each time a request is changed or updated, recording details of the changes

Associating users with requests

• When a change request, action log or change request audit log is created, it is now associated with the current user (or for action logs, the creator of its associated change request)

Project Navigation

• Adds a side bar for navigating between projects. These are grouped into active and archived projects
• For archived projects, the create and manage events pages are not present (as no events possible)

Permission Updates

• Pundit policies are added for more project related pages and added for change request related actions
• Viewer users are now prevented from accessing the create/edit event wizard and links to these pages are not shown to them on the manage events page

[ColonelPanicks]

Looks like description field doesn't handle punctuation kindly

[ColonelPanicks]

Another thing - Descrtiption doesn't appear in slack notifs or the manage events screen. Probably worth including it if it's present?

[timalces]

This branch has now been significantly updated after the merge of #19, and now also addresses #20 and #21

[timalces]

Merging this as appears to be working as expected.