optimize camera upload service

Optimize camera upload service to keep itself running and responding as long as possible.
When OS unders memory pressure, it will kill the service to save CPUs and resources for the foreground applications. In this case camera upload service will be killed at the same time, though OS will restart the service later when has enough memory, it doesn`t guarantee to response to Camera event any longer (when photo taken, no uploading task invoked). This PR is targeted to handle this problem.

But there are still have some problems to handle.
1. In settings menu, Gesture Lock doesn`t work properly when user go back to the app by multitasking window.
2. Plan to restart the app after system boot again, so register to listen to OS boot broadcast, in order to start camera upload service when boot completed. Have tested the function via Galaxy Tab P3110 and XiaoMi2A, both passed, but Huawei G610. So this function was removed in this PR.