Add Set Server/Channel Group context menus and dialog

Lets moderators assign or revoke server and channel groups for a
client directly from its context menu, with per-group checkboxes
gated by the client's actual TS3 permissions (i_group_needed_member_
add/remove_power vs. each group's n_member_addp/removep, including
TS3's -1 "unlimited" sentinel). A "Server Groups Dialog..." entry
shows every server group, graying out ones the client can't touch.

Group membership changes now update ClientEntry locally instead of
only logging them, so the checkboxes and dialog reflect a change
immediately instead of needing a reconnect. The server's default
channel group (e.g. "Guest") is hidden from the channel-group menu
since it's not something you assign directly.

ts3-client/swing/src/main/java/com/ts3client/ui/ServerTab.java

@@ -69,7 +69,7 @@ final class ServerTab implements ServerTabConnectionEvents.Listener {
         this.groupIcons = new GroupIcons(conn.getIcons());
         this.selfState = new ServerTabSelfState(conn);
         this.chatPanel = new ChatPanel();
-        this.treeActions = new ServerTabTreeActions(host, this, conn, chatPanel, infoPanel);
+        this.treeActions = new ServerTabTreeActions(host, this, conn, chatPanel, infoPanel, groupIcons);
         this.treePanel = new ServerTreePanel(conn.getModel(), groupIcons, treeActions);
         treeActions.attach(treePanel);
         events.attach(conn, treePanel, chatPanel, selfState, treeActions);