Added foreground service to process files instead

[ajakka]

I just added a foreground service with a persistent notification that displays the progress of files, and when It ends, The user can click on the notification to show the file share dialog.

What's still missing:

• This current commit doesn't fully update the HandleMediaActivity, although the Service does communicate with the Activity via a Binder, It just returns the progress for now. I might add the rest later and replace the binder with LiveData.

[caydey]

First off, thanks for putting in the time of making such a large change to the code base. I've got some changes that I think would make the app run smother:

• The compression should not automatically be taken to the background
• It should be entered if the user clicks a button on the compression progress screen or loses focus of the App

[ajakka]

I actually wanted to do this initially but I couldn't find a way to resume the work from the activity to the service, but I'll double check If I find a way.

also I'll switch to using Live data instead of bindings

When I have some spare time