[Core/WebSocketLink] : Enable unsollicited 'Pong' and rename enum item

[msieben]

• Rename 'WEBSERVER' to 'WEBSERVICE' as both client and server utilize state information

• Unsollicited 'Pong' may act as a heart beat

[pwielders]

@msieben the enum is a public interface. You can not change it in one go. Support both, deprecate the old one and in a next Major Release we can drop it. This should not go in 1 go. Code might depend on this enum value.
Please also refer to a ticket this is solving..

[pwielders]

Keep on supporting the "old enum" value, add the new enum value and use the DEPRECATE keyword on the old enum value so code will raise a warning that the enum needs to be changed. In the next Major Release we can drop it than.