This is required in segmented scenarios when multi-threaded where the same `track.path` would be get and set from possibly at the same time. It's also just better logically to do it this way.
The new system now downloads and decrypts segments individually instead of downloading all segments, merging them, and then decrypting. Overall the download system now acts more like a normal player.
This fixes#23 as the new HLS download system detects changes in keys and init segments as segments are downloaded. DASH still only supports one period, and one period only, but hopefully I can change that in the future.
Downloading code is now also moved from the Track classes to the manifest classes. Download progress is now also actually helpful for segmented downloads (all HLS, and most DASH streams). It uses TQDM to show a progress bar based on how many segments it needs to download, and how fast it downloads them.
There's only one down side currently. Downloading of segmented videos no longer have the benefit of aria2c's -j parameter. Where it can download n URLs concurrently. Aria2c is still used but only -x and -s is going to make a difference.
In the future I will make HLS and DASH download in a multi-threaded way, sort of a manual version of -j.
If the manifest is hidden behind a redirect, the url is not updated and the segments are created with the old url.
I found a French service where this situation occurred.
After this change, it was possible to correctly parse the mpd.
