Adds "use fmp4" experimental option

[sul4bh]

Fixes issue #610

Adds a new experimental option that makes the native player use fmp4 segment container instead of ts. HEVC/HDR is only supported in fmp4 stream as documented here: "The container format for HEVC video MUST be fMP4.", https://developer.apple.com/documentation/http_live_streaming/http_live_streaming_hls_authoring_specification_for_apple_devices

FYI, fmp4 setting is already available in the web client:

The new experimental option

HDR now works as expected on my Apple TV

[sul4bh]

Not sure why tests did not run for this PR.

[LePips]

That's just due to #562, which is fine. Carthage is broken right now and should anticipate a fix soon.

I'm glad that the change is small to get HDR with the native player. Since it's so small and technically a proven "feature-that-works" I'll most likely make it an option in my current work and it won't remain in experimental, also because I've refactored the view model that is used but I won't bother you with worrying about that.