Small cleanup.
First pass at a behavior bake task.
Fix issue when test suites have no tests.

In this situation a fatal error would be raised as the type hint for
FixtureManager would be violated as PHPUnit passes a warning object to
test listeners.
Fix up behavior task and add tests.
Hook behavior bake into BakeShell.
Fix mistake.
Merge pull request #3217 from markstory/3.0-behavior-bake

3.0 behavior bake