Removed a few conditions from IsSocketConnected that have been moved to IsConnected. Fixed a few warnings.
Remove commented code.
Renamed ChannelAsyncResult.cs to CommandAsyncResult.cs to match name of class.
Removed command argument from CommandAsyncResult as its never used.
Fix some warnings.
Also create source zip file as part of build.
Improved accuracy of IsConnected on .NET.
Fixed typo in remarks.
Added support for ssh.com private keys.
Fixes issue #1987.