Added switchToTimeline() method.
Don't seek to values lower than 0.
* pitivi/timeline.py:
Add default sources behaviours in compositions.
Added setDefaultSource() and getDefaultSource() methods.
* pitivi/ui/complexinterface.py:
pixelToNs should return a long (to cope with 2**64 values).
* pitivi/ui/complexlayer.py:
Don't expand audio tracks at startup.
* pitivi/ui/ruler.py:
Allow seeking on the ruler.
* pitivi/ui/sourcefactories.py:
Use the source thumbnail as the icon pixbuf when doing drag and drop.
* pitivi/ui/timelineobjects.py:
Switch to Timeline in the playground if we drop something in it.
* pitivi/ui/viewer.py:
Use bilinear scaling method with videoscale.
Use videosink pad to figure out caps modifications.


git-svn-id: svn+ssh://svn.gnome.org/svn/pitivi/trunk@801 d3729300-e425-0410-8a4c-d956edccc248