Feature: Optionally wait for initial delay

[jpettersson]

Hey!

Thanks for the great work on this app!

I wanted to record a timelapse of wild animals early in the morning and needed a way to automatically start the timelapse at a given time. The quickest solution I came up with was to add a delay feature to your app, to allow the user to select a delay before the timelapse recording begins.

The additions to the UI are:

• SettingsActivity: A delay slider using the same AdvancedSeekBar
• ShootActivity: Re-purposing an existing TextView to show the delay countdown

I've tested the app successfully on my a6500 (and yes, I did capture some animals in the timelapse :)

I tried to follow your UI design and code structure to make the change possible to merge, in case you find it useful.

Best regards,
Jonathan