Add wishlist pages

* Add wishlist pages.
* Set 'trade' checkbox in add to playlist/wishlist to checked by
default.
Add feedback pages

* Add public/user versions of feedback page.
* Users can send feedback.
* Send mail to admin account when user posts feedback.
* Change navbar colour of public pages to that of user navbars.
:lollipop: Add add trade page

* Users can add trades!
Add trades page

* Add sort order to locations, games and trades so that freshest
entities appear at the top.
* Add exceptions so that trades are deleted before locations/games for
now.
* Add trades page.
Add missing trades page

* Add trades page missing from previous commit.
* Add delete trade feature.