Make Oracle Locks check much more useful

Currently mk_oracle plugin, section Oracle_Locks has a sql-clause that produces information about session, lock time, SID, machine, serial, process and os user.

However as most Oracle application users are behind a web or application server nowadays maybe the MOST important information - id/username of the blocker - is not displayed. This is the information Oracle DBA's and/or people monitoring the locks need the most (unless they just brutally kill the session belonging to the blocker).

In the current sql-clause there is a field (perhaps if you would do your own custom plugin) _dbuser but even this info is about the blocked user, NOT the blocker !!

As it is now, this check basically only tells you that there is a lock in database, but you mostly cannot tell who is causing it without logging into that database and run a (better) query for it. And that's really wasted time.