Draft: Redesign homepage

following @mdelafuente's design: https://phabricator.kde.org/M187/719/

At the top we have this list of featured apps, this is good to give emphasis on some specific applications.

Then we have some category areas displaying up to 9 apps, if the window is big enough it'll show an grid otherwise it'll show a list.

These changes are great because they increase the card density on the desktop and differentiate the featured apps from the top rated apps from each category.

Why this is a draft?

• featured cards shouldn't be this wide, the description text isn't elided or wrapped (ideally it should wrap to a second line but elide before an third line)
• featured cards list should have navigation controls
• cards layout isn't good enough
• "See More..." button doesn't do anything
• I should probably change the ApplicationDelegate to look like this when in compact mode
• page padding isn't consistent with other pages

I'm having a lot of problems trying to fix these issues, any help would be very appreciated :)

@teams/vdg and pinging @carlschwan since this backend code was done by him