Move downloaded projects to the top of the list

[saberraz]

When a project gets downloaded, it would be good to have it moved to the top of the list in the QGIS Browser panel. If you have a long list of projects, you need to scroll all the way down to find it in the list. Related to #218

[erpas]

This is done but works incorrectly as the downloaded projects list is created AFTER pagination. As a consequence the list of downloaded projects grows when users double-click for more projects.