RFR: 8151181: Add JSnap to jhsdb

[Yasumasa Suenaga]

Hi all,

JSnap is useful SA tool to check PerfCounter. 
So I want to add it to jhsdb.

  http://cr.openjdk.java.net/~ysuenaga/JDK-8151181/webrev.00/

Could you review it?


Thanks,

Yasumasa