add a welcome view

- the loadview is now a welcome-style view
- the recent media list has moved from the loadview into the
krecentfiles tech in the menu
- the three play actions are now actual qactions
- the play actions are grouped together in the menu instead of using the
loadview as meta-open view this gives more immediate access to the
actions from anywhere in the app, is more in line with other
applications and frees up the loadview to serve only as welcome view (to
be shown when indeed nothing is playing at all)
- the unused playdialog is no more; along with the newly unused
recentlyplayedlist