Update docs for Shell folder location.
migration note
Fix typo
Correct wording
Fix eg. code.
Merge pull request #1658 from antograssiot/3.0

3.0 use ``true``/``false``
Update routing.rst
Merge pull request #1662 from vttn/patch-2

Update routing.rst
Merge pull request #1636 from cakephp/3.0-shells

Update docs for Shell folder location.
Fix example.
update docs for command line format