[Linux] File open dialog inconsistent / too simple

The 'file - open' dialog in Musescore 2.0 rev e9e0e34 on Ubuntu 14.04 is missing some standard features, like bookmarked directories. In the same Musescore the file dialogs used in the preferences window are correct and feature the bookmarked directories.

See the screen shots here: http://musescore.org/en/node/27251