Add reverse flamegraph view

I usually find a reverse flamegraph (a.k.a. icicle graph) much more useful than the current table representation. The hottest methods are often JDK or other library methods that you can't change directly. But you can find out which of your methods are calling those hot methods by going up a few frames.

My suggestion would be to completely replace the table view with a reverse flamegraph. But if other users like the table, then it could also be a toggle.