Wayland API to get the id of focus window [Seema Singh]

[Bill Spitzak]

Seema Singh wrote:

> Focus window pid is used for below check:
> 1. If focus window APP is not a NFC APP then launch the NFC APP
> 2. If already launched but not in focus then bring it to foreground.

The NFC app should always launch, but then it should just check if it is 
already running, and if so tell the other one to raise and then exit.