manual: add some text about bin state change order
manual: add some text about bin state change order

shelsonjava/gstreamer,ensonic/gstreamer,jpxiong/gstreamer,mparis/gstreamer,jpakkane/gstreamer,justinjoy/gstreamer,lubosz/gstreamer,jpakkane/gstreamer,ensonic/gstreamer,lubosz/gstreamer,ensonic/gstreamer,krieger-od/gstreamer,lubosz/gstreamer,surround-io/gstreamer,collects/gstreamer,shelsonjava/gstreamer,centricular/gstreamer,shelsonjava/gstreamer,Lachann/gstreamer,lovebug356/gstreamer,StreamUtils/gstreamer,mparis/gstreamer,centricular/gstreamer,lovebug356/gstreamer,krichter722/gstreamer,krieger-od/gstreamer,StreamUtils/gstreamer,justinjoy/gstreamer,lubosz/gstreamer,collects/gstreamer,centricular/gstreamer,lubosz/gstreamer,cablelabs/gstreamer,mparis/gstreamer,StreamUtils/gstreamer,collects/gstreamer,surround-io/gstreamer,cfoch/gstreamer,jpakkane/gstreamer,ensonic/gstreamer,jpakkane/gstreamer,cablelabs/gstreamer,justinjoy/gstreamer,surround-io/gstreamer,StreamUtils/gstreamer,jpxiong/gstreamer,centricular/gstreamer,justinjoy/gstreamer,krichter722/gstreamer,krieger-od/gstreamer,jpxiong/gstreamer,mparis/gstreamer,cfoch/gstreamer,mparis/gstreamer,krichter722/gstreamer,collects/gstreamer,lovebug356/gstreamer,cablelabs/gstreamer,lovebug356/gstreamer,jpxiong/gstreamer,Lachann/gstreamer,surround-io/gstreamer,cfoch/gstreamer,ensonic/gstreamer,justinjoy/gstreamer,surround-io/gstreamer,lovebug356/gstreamer,krichter722/gstreamer,Lachann/gstreamer,krieger-od/gstreamer,Lachann/gstreamer,centricular/gstreamer,shelsonjava/gstreamer,collects/gstreamer,cfoch/gstreamer,cablelabs/gstreamer,StreamUtils/gstreamer,krichter722/gstreamer,cablelabs/gstreamer,cfoch/gstreamer,krieger-od/gstreamer,Lachann/gstreamer,shelsonjava/gstreamer,jpakkane/gstreamer,jpxiong/gstreamer