Implement individual MP policy positions page

Part of #359, displaying a complete list of MP policy positions. Also implements a reduced number of positions on MP profile pages, and moves policy listing to a new class.

* Closes #378

## To Do

* [x] Fix strange padding on MP pages side menu
* [x] Remove H1 on votes page
* [x] Add MP name to all segments
* [x] Add segments title links
* [x] Fix horizontal tab colours

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