Retrieve and display dynamically Qt Academy content

The Academy content is static, no new courses are visible if they are released after the feature freeze of Qt Creator.

Qt Creator shall retrieve an up to date list of Academy content and present them in descending publishing order. Additionally, Qt Creator shall allow the user to toggle between alphabetic and chronological order as the sorting mechanism. Optionally, Qt Creator shall cache the list of Academy content items and present them if the API is not reachable (however, browser is responsible for displaying errors in accessing). Also: evaluate whether it makes sense to rename the learning categories.

The API documentation is available from the vendor: https://docs.learnupon.com/api/#learnupon-api-guide 

The API uses basic authentication and there's no scoping or other constraints to restrict its usage. Hence a shim interface inbetween Qt Creator and the actual API would prevent misuse and also enable caching outside of Qt Creator. 

Acceptance criteria: 

Qt Creator displays the most recent Academy courses.  Qt Creator allows the user to select the sorting criterion for Academy content.

(Qt Creator shall display cached content if there is no network connectivity.)