* Add a big back button in details page.
* Add static CSS to render QPushButtons as flat when the `flat` property is set
* Remove outer scroll areas from details page since the page is already adjustable
* Remove scroll area from the requirements widget because ElideLabels are already used in it.
* Fix crash when sorting the wishlist
Important changes:
* Refactored QtRequests to accept parameters for `GET` operations
* Infer response data type from content-type header
* Support caching to disk, a manager with this set prefers the cache
* Support multiple handlers for a single request (unused, possibly pointeless)
* Subclass `ShopImageWidget` for all widgets used in the shop
* Request a resized image instead of the original one
* Fix the search and browse functions
