Make some rows activatable

This MR simply makes artist_row and song_row activatable and adds to them functionality of buttons, that already located there. Drag and drop to reorder songs in playlists still works though. Also removes border on button on artist_row to be more like others suffix buttons found on other rows (don't think this change deserves it's own MR, so here it is).

As for the reason why, I find it's tough to snipe those buttons with touchpad.