Compositor: do not delete the CompositorWindow object directly in closeWindowWithId

Signed-off-by: Christophe Chapuis <chris.chapuis@gmail.com>
WindowModel: when adding or removing a window, group the processing to synchronize the signals as much as possible

Signed-off-by: Christophe Chapuis <chris.chapuis@gmail.com>
WindowModel: add a "count" property

Signed-off-by: Christophe Chapuis <chris.chapuis@gmail.com>
Merge pull request #69 from webOS-ports/tofe/work

Tofe/work