A bunch of cleanup

[codemonkey85]

• Use GeneratedRegex where possible
• Use file-level namespaces
• Use global usings
• Use new C# features such as collection expressions and primary constructors
• Fix spelling errors (mostly 'precent' instead of 'percent')

[shaked6540]

Hey, thanks for the help, however I see that theres a lot of spaces or tabs that got replaced and it shows every file as changed as a result, can you tell me which files you changed? (except the using)

[codemonkey85]

Sure.

• The generated RegEx is used in
  • YoutubePlaylistDownloader/Utilities/YoutubeHelpers.cs
• Primary constructors are used in
  • YoutubePlaylistDownloader/Objects/FixedQueue.cs
  • YoutubePlaylistDownloader/Objects/FullPlaylist.cs
  • YoutubePlaylistDownloader/Objects/QueuedDownload.cs
• Array expressions are used in
  • YoutubePlaylistDownloader/DownloadSettingsControl.xaml.cs
  • YoutubePlaylistDownloader/GlobalConsts.cs
  • YoutubePlaylistDownloader/MainPage.xaml.cs