.NET: Document .NET Core support and running on Linux / macOs

Create a documentation page about running Ignite.NET under .NET Core and/or Linux. Things to mention:

• Delegates can't be serialized under .NET Core: https://github.com/dotnet/corefx/issues/24424
• Build warning - suppress NU1701 with <PropertyGroup><NoWarn>NU1701</NoWarn></PropertyGroup>
• Java home, dll paths, etc
• Publish and deploy (copy libs folder to dotnet publish dir)
• macOs: document No Java runtime present, requesting install. issue https://bugs.openjdk.java.net/browse/JDK-7131356, https://github.com/s-u/rJava/issues/37
• VS Code and Rider
• Mono is supported (useful for 32 bit and/or older distros): need to set IgniteHome, need sudo apt-get install mono-reference-assemblies-4.0 to build
• <PackageReference Include="System.Configuration.ConfigurationManager" Version="4.4.0" /> may be required
• Make sure examples in binary package can be run on Mono and .NET Core on every OS.