* Fix warnings, improve performance
`QueryResult.Items` is now a `IReadOnlyList` so we don't need to
allocate a new `Array` when we have a `List` (and `Items` shouldn't need to
be mutable anyway)
* Update Providers .csproj to latest C#
* Remove extra newline from DtoService.cs
* Remove extra newline from UserLibraryService.cs
Use the username to construct the UserConfigurationDirectory,
instead of the user ID, and move the old ID-based path to the new
path if needed when loading (temporary transitional code). Removes
administrator guesswork as to what user each directory belongs to,
which I found very annoying when investigating user configs.
* Remove some unused variables
* remove duplicate "using .." by sorting and deduping the list
* Remove things that already exist in the parent class (in one case I moved some documentation to the parent)
* EntityBodyData and and NextSearch were never set (only read), removed
* _timeout was never read, subsequently _timer became unused. part of a TODO timeout functionality that was not implemented yet
**Changes**
Fixed a faulty change in logic that occurred during the Christmas GPL nightmare.
I stepped through Emby 3.5.2 and stumbled over a difference in the query between Jellyfin and Emby, where in Emby, query.ParentId was set to the item itself. So I did a little digging in the old GPLv2 source and found this https://github.com/MediaBrowser/Emby/blob/3.4.1.8/MediaBrowser.Controller/Entities/Folder.cs#L720
**Issues**
Fixes#673
Bond_009
dkanada
Anthony Lavado
SL1288
Andrew Rabert
Anthony Lavado
Joshua M. Boniface
Claus Vium
Claus Vium
Torsten
Vasily
Erwin de Haan
hawken