Reactions map should use enum as a key

[kestivvi]

In WebSocketSplendorServer class there is the reactions field (See the codeblock below). It maps type of request (string) to the appropriate reaction class (request handler). It's safer to use enum as a key, there is created ReactionType enum for this purpose.

Changing this involves tinkering with ReactionManager class and it uses reflection a lot. It's an relatively easy task, but you have to know reflection a bit.

ServerSide/src/main/java/com/github/splendor_mobile_game/websocket/communication/WebSocketSplendorServer.java

Lines 24 to 27 in da9b9de

	public class WebSocketSplendorServer extends WebSocketServer {
	private Map<String, Class<? extends Reaction>> reactions;