Remove non-standard installation instructions.

Suggesting people monkey around with the installation paths will only
cause issues down the road.
Start updating the controller docs.
Fix some duplication in request/response docs.
Update response docs.

Remove API section and put method links inline.
Add view variables section.
Remove pointless docs.

This should be covered in the API not the book.
[fr] follow cbf07f8

Fix build warnings.
Fix event class name
Merge pull request #1522 from matthieuy/patch-1

Fix event class name
Update cakephp-structure.rst

JsHelper has (unfortunately IMHO) been removed from the core, so this info is now outdated.
Merge pull request #1524 from oldskool/patch-5

Update cakephp-structure.rst
Update views.rst

Removed another JsHelper reference, since JsHelper was removed from the 3.0 core.
Merge pull request #1525 from oldskool/patch-6

Remove JsHelper reference
Make corrections from feedback.
Merge pull request #1523 from cakephp/3.0-cleanup

3.0 cleanup