Start adding summary features.

Add summary method to base class and implement it in the LogPanel. The
summary method is intended to return bite size amounts of data that give
some high level answers. For example, were there any log messages this
request, or how much memory/time did the request take, or how many
queries were run.
Add summary to sql log panel.
Add summary to timer panel.
Add summary to saved panel data.
Add summary output.
Style summary data.
Fix mistake in sqllog panel.
Fix failing tests caused be exception renames.

A bunch of tests started failing because of exception class renames.
Merge pull request #210 from cakephp/summary-data

Summary data