Start work on offline download support

[BenStokmans]

This PR was inspired by @JacobKingDev. It improves upon the current framework for media downloading provided by @LePips. It is far from finished, and I intended to improve on it in the coming weeks. I would love any feedback, as this is the first time I'm working with Swift, so my code is probably riddled with nonsensical rubbish. That being said here is a list of the changes I've implemented.

• Fixed negative percentage with progress text while downloading (the way I get the excepted size is kind of hacky, I would love pointers on how to improve it)
• Improved design of download list view
• Added size label to download item view (added extension to the FixedWidthInteger extension)
• Added temporary OfflineTabCoordinator for testing I'll try to integrate it with the MainTabCoordinator ASAP
• Changed the default behaviour when a NSURLErrorNotConnectedToInternet to showing a view using the OffileTabCoordinator.
• Added the ability to remove downloaded media

[LePips]

I'm glad that this is able to pick up starting from my latest work, but is there a reason why we didn't ask on the previous draft PR to continue the work elsewhere?

[BenStokmans]

I'm sorry I don't quite understand what you mean by:

but is there a reason why we didn't ask on the previous draft PR to continue the work elsewhere?

[LePips]

There is already a pre-existing PR for working on downloads. While it has been a while since work was done on it, and that's okay, now we have 2 PRs for the same feature.

I'm going to have to ask you to communicate with @JacobKingDev about taking over the feature, or at the very least it would have been nice ask if there was interest to continue the previous work. Even if after a few days there isn't an answer, then another PR would have been fine.

[BenStokmans]

@LePips I have asked in the previous PR, but I'm yet to get a response. In a mean time, I've completed a very rough version of my idea of the downloads section. It can be enabled in the experiments section, and I'd love some feedback on how you think it looks and feels. The code for the UI is largely a verbatim copy of the ItemView group (there is a lot of duplicate code that can be removed) the reason I did it like this is I wanted to match the current design as much as possible. If you have any feedback on the rest of the code or the way I've decided to handle the downloads, please let me know.

What currently works:

• Downloading any episode or film
• Both online and offline playback of downloaded media
• Properly grouping episodes on season and series
• Resume items, Next up items and adjacent items for downloaded media

What doesn't work (yet) / what I haven't got around to:

• Playback progress syncing
• Estimated time left on download
• Batch downloading (e.g. season)
• Proper support for different users
• Picking specific media source

[LePips]

It will take me a while to look at this as I work on the video player again. Due to that, I see that some things will probably have to be rewritten, but I don't anticipate it to be too much. I will also have to think a lot about the overall architecture that my initial work had and whether it needs to be redone.

[chickdan]

With two forks already and multiple folks wanting to pitch in (myself included), I think it would be helpful to have these PRs put into a feature branch until it's ready for main. Ideally we will see smaller change-sets, too.

[BenStokmans]

@chickdan I would like that. If you want to make a feature branch, I would be happy to contribute.