Adds a dropdown to the user's profile preferences, allowing the user to choose a default view for the project's issues.
The user can choose either the issues list, or the new board view.
The choice is reflected by dynamically changing the link to the Issues page in project views.
Are there points in the code the reviewer needs to double check?
There may be a better way to do the changes in app/views/layouts/nav/_project.html.haml
Please let me know if so.
I also had trouble finding the correct existing test suites to add tests to.
Why was this MR needed?
In addition to the points outlined in #21304 (moved), the new board view is very useful, to the point of superseding the issues list.
This MR allows the user to skip the issues list.
