[VD] add Gaming hub feature
In the gaming hub panel,
there is a scenario where webapp plays sound after background launch.
Also, it should be possible to switch to UI mode.
At this time, must support multitasking unconditionally.
Add three fetures to support this.
1. Transition of FG and BG through Appcontrol
2. disable multitasking feature according to special App Control.
3. window's hide is required for Appcontrol BG transition. (change WebEngine code)
Change-Id: If6760ab87ece3966599cab5f393d043467b39187
Signed-off-by: yman.son <yman.son@samsung.com>