Fixed getAmountOfServerGroups and implemented getClientServerGroups

getAmountOfServerGroups:
get(ClientProperty.CLIENT_SERVERGROUPS).length() returns the doubled servergroups because of the comma
But because there is always one comma too less I added 1 to get(ClientProperty.CLIENT_SERVERGROUPS).length() and then divided it. getInt was turning the String 1,2,3,.. to a int which wasn't right.

getClientServerGroups:
getClientServerGroups returns a string containing the server group ID for example 1,2,3,...
Updated getAmountOfServerGroups()
Update ClientJoinEvent.java
Update ClientJoinEvent.java
Update ClientJoinEvent.java
Fixed getAmountOfServerGroups and implemented getClientServerGroups

Now getAmountOfServerGroups works even if the id of the servergroup is <=10
Merge pull request #25 from Raavgo/patch-1

Patch 1