plugins: only add windows with correct type to window model

Signed-off-by: Simon Busch <morphis@gravedo.de>
plugins: set the WindowType of the launcher to Launcher

Signed-off-by: Christophe Chapuis <chris.chapuis@gmail.com>
Merge pull request #67 from webOS-ports/tofe/work

Tofe/work
plugins: split intro three parts: common, shell and compositor

Signed-off-by: Simon Busch <morphis@gravedo.de>