Adjustments for compiling and developing on Linux

[ViToni]

Renamed files to match class names and case sensisitive file system on Linux:

• SimpleDLNA/StartupUtilities.cs
• server/Http/HttpServer.cs
• server/Types/Subtitle.cs
• util/FFmpeg.cs

Changed files to match case sensitive paths / names:

• SimpleDLNA/FormMain.cs
• server/Http/HttpClient.cs
• server/Properties/Resources.resx
• util/util.csproj

[nmaier]

I'm not to keen on the pull request also containing a SQLite nuget update, in particular one that breaks the setup project.

[goblin]

Thanks @ViToni, this helped me compile on Linux as well. I also had to rename some filenames due to case sensitivity:

 rename server/Http/{HTTPServer.cs => HttpServer.cs} (100%)
 rename server/Types/{SubTitle.cs => Subtitle.cs} (100%)
 rename util/{Ffmpeg.cs => FFmpeg.cs} (100%)

[ViToni]

I'm not to keen on the pull request also containing a SQLite nuget update, in particular one that breaks the setup project.

Reduced the PR to the minimal changes to make it compile without warnings on Linux.
All dependency updates have been removed.