plugins: change preview source when plugin is loaded

...oid/app/src/main/java/cx/ring/fragments/CallFragment.java

...oid/app/src/main/java/cx/ring/tv/call/TVCallFragment.java

...d/app/src/main/java/cx/ring/views/AutoFitSurfaceView.java

ring-android/app/src/main/res/layout/frag_call.xml

ring-android/app/src/main/res/layout/tv_frag_call.xml

...bringclient/src/main/java/cx/ring/call/CallPresenter.java

...id/libringclient/src/main/java/cx/ring/call/CallView.java

...libringclient/src/main/java/cx/ring/model/Conference.java

...lient/src/main/java/cx/ring/services/HardwareService.java