welcome timestamp replace with readable date time

bin/as.sh

@@ -467,7 +467,7 @@ main()
     echo "Attach success."
 
     if [ ${ATTACH_ONLY} = false ]; then
-      echo "Connecting to arthas server... current timestamp is `date +%s`"
+      echo "Connecting to arthas server... current time is `date '+%Y-%m-%d %H:%M:%S'`"
       active_console ${arthas_local_version}
     fi
 }

core/src/main/java/com/taobao/arthas/core/shell/impl/ShellImpl.java

@@ -21,6 +21,7 @@ import com.taobao.arthas.core.shell.system.impl.JobControllerImpl;
 import com.taobao.arthas.core.shell.system.impl.JobImpl;
 import com.taobao.arthas.core.shell.term.Term;
 import com.taobao.arthas.core.util.Constants;
+import com.taobao.arthas.core.util.DateUtils;
 import com.taobao.arthas.core.util.LogUtil;
 import com.taobao.middleware.logger.Logger;
 
@@ -119,7 +120,7 @@ public class ShellImpl implements Shell {
         if (welcome != null && welcome.length() > 0) {
             term.write(welcome + "\n");
             term.write("pid: " + session.get(Session.PID) + "\n");
-            term.write("timestamp: " + System.currentTimeMillis() + "\n\n");
+            term.write("time: " + DateUtils.getCurrentDate() + "\n\n");
         }
         return this;
     }