Fix additional, pointless and sometimes harmful inflections.

Since CakePHP 3.0's conventions are that most things are plural, we
don't need to be pluralizing things as people will be thinking in terms
of plural forms. Removing this code from bake makes it much easier to
accomodate names like menus without incorrectly inflecting them.

Fixes #4647
Merge pull request #4737 from cakephp/issue-4647

Fix additional, pointless and sometimes harmful inflections.