Fix Typo and add information to Handling quit requests/On mobile devices

[ztc0611]

There is a minor typo where the entirety of "Application > Config > Quit On Go Back" is not bolded, and the important information about app process killing on iOS that can be seen in the docs for NOTIFICATION_APPLICATION_PAUSED should likely be pulled into this section.

Both of these changes are relevant to 4.3's docs.