Support JDK7 omitted exceptions

[hlship]

JDK7 adds the concept of an "omitted exception" which is related to the try with resources construct. These are still valuable, still part of the cause train.

JDK7 .printStackTrace presents omitted exceptions somewhat "side-barred", indented under the exceptions they were collapsed into. We could do the same, or use an alternate (dimmer) font for such exceptions.

Since we only present the stack trace of the deepest exception, even that may not be necessary.