qml: Add the 'My Folders' section in the Browse tab

This MR adds a dedicated "My Folders" section with a selection of the most common standard paths.

We are including the following default paths:

• Home (Unix)
• Desktop
• Documents
• Music
• Movies
• Download

This MR also adds a helper template class for sorting and filtering QAbstractListModel item(s). We tried implementing capping from a QSortFilterProxyModel and QML, but both implementations had flaws:

• The QSortFilterProxyModel has a filterAcceptsRow function, but it does not work for an item capping scenario.
• Regarding QML we found ways to make it work, but it felt hackish and brought up issues on our items shadows.

Although a pure QML implementation could be done, a C++ implementation is probably more elegant. Especially now that we are using a template that can fit several use case scenarios.