fix(logging): Summarize SKIPPED tests in debug.html.

Before: hundreds of SKIPPING lines in console.log.
After: A single summary line with a count.

Closes #1111
Indeed, these annoying messages force you to pay attention to tests that you have deliberately marked as not important. The deliberate act of marking tests to be SKIPPED is a signal that Karma should obey. The common case of marking tests to be skipped is the use of `ddescribe()` or `iit()` to isolate a single suite or test for debugging or analysis.  But such debugging or analysis is more difficult than necessary when the console is filled with hundreds of lines of SKIPPED tests.

Occasionally a developer uses `xit()` to skip a single test while investigating some other problem.  The summary line at the end of the Karma run reminds the developer to return to this case.