Remove duplication in file header.
Remove unused method.

This method is no longer useful and can be removed.
Extract a conventions trait.

Having a trait with some commonly used inflections/conventions makes the
Shell class a bit cleaner and contain less junk. Having a trait also
allows userland code and other parts of the framework to re-use this
piece.
Fix failing test.
Merge pull request #3204 from cakephp/3.0-shell-cleanup

3.0 shell cleanup
Start Helper bake task.
Extract SimpleBakeTask

HelperTask and BehaviorTask were so similar that their differences could
be expressed as simple set of properties.
Update other bake tasks to use newer style path generation.

Fix incorrect help text.
Hook helper task into BakeShell.
Add template and task for component generation.
Collapse Helper and Behavior task tests together.

These classes have all their code defined in the super class, so there
is no reason to maintain double the test cases.
Use an abstract class instead of public properties.

Having an abstract class will make the bake task collector much simpler
as it we can detect base classes like SimpleBakeTask. Having methods
means implementations could use custom code if they wanted.
Add additional imports people are likely to need.
Wire component bake into BakeShell.

Fix merge conflict mistakes.