Added header file and converted ConsoleFunction to DefineEngineFunction

I added a header file for Net.CPP and converted the legacy ConsoleFunctions to DefineEngineFunctions.

I also converted these to DefineEngineFunction:
-commandToServer 
-commandToClient
-DefineEngineFunction
-addTaggedString
-removeTaggedString
-getTaggedString

I left the following as ConsoleFunction
-buildTaggedString