This patch changes the version numbers of the plugins to 2.0. This
includes the previously 0.1 plasmacomponents, extras and
qtextracomponents. DragandDrop, which was at 1.0 is now also at 2.0.
Also, all the QML code has been changed to import the 2.0 plugins.
As a side-effect, we now share a version number with QtQuick 2.0 now.
All cpp code moves into the src/ subdirectory, as the Frameworks policy
suggests.
Directory structure should now be in line with other, future frameworks.
