Undertow mod_cluster CLI: Display node's Elected, Read, Transferred, Connected stats

As a follow up to JBEAP-215, this bug report is a member of a series addressing crucial CLI management capabilities.

Implement & Display node's Elected, Read, Transferred and Connected stats

At the moment, this is all there is to see:

"balancer" => {
    "qa_balancer" => {"node" => {"worker-2" => {
        "load" => 89,
        "status" => "NODE_UP",
        "context" => {"/clusterbench" => {
            "requests" => 0,
            "status" => "enabled"
        }}
    }}},
...

Furthermore, at a glance, it appears that a part of the needed stats is a mere placeholder at the moment: NodeStats.java

Call to action

Display the aforementioned stats for each node. Let me set priorities according to what is really used in the battlefield:

• Critical: Elected (it is often correlated with Load during load metric history and capacity tuning)
• Minor: Read
• Minor: Transferred
• Minor: Connected