Add ShellTask for generating shell class stubs.
If names are empty error out.
Add support for generating Shell command test cases.
Fix tests that fail when bake tasks are added.
Remove uneeded namespace registration for class loader.

With composer loader now being used for tests too the extra loader
registrations are not required.
Merge pull request #3361 from ADmad/3.0-tests

Remove uneeded namespace registration for class loader.
Merge pull request #3359 from cakephp/3.0-shell-bake

3.0 shell bake
Use composer installed PHPUnit vs. whatever is on travis.ci

Lock down to an older PHPUnit until we can get session code re-written.
The latest PHPUnit 3.7.x breaks session support which we need for the
time being.
Merge pull request #3367 from cakephp/travis-phpunit

Use composer installed PHPUnit vs. whatever is on travis.ci
Fix path related failures in bake tasks.