3.0 migration guide for personId()
Merge pull request #1546 from dereuromark/3.0-validation

3.0 migration guide for personId()
Update config folder path.
Fix incorrect config file name.
Missed one.
Fix build errors and warnings
Update Xml and String docs.
Update more docs

* Fix code samples
* Add headings to make TOC scanning simpler.
Update a few more chapters.
Merge pull request #1549 from bcrowe/3.0-build-errors

3.0 - Fix build errors and warnings
Merge pull request #1547 from cakephp/3.0-config-folder

Update config folder path.
Merge branch '3.0' into 3.0-proof-pt4

Conflicts:
	en/installation/url-rewriting.rst
Fix mistakes and add stackTrace() function.
Update info regarding removed functions.
Fixed var name casing.
Merge pull request #1551 from cakephp/3.0-proof-pt4

3.0 proof pt4
Merge pull request #1552 from cakephp/3.0-basic-funcs

Update info regarding removed functions.
Fix comments
remove capital of multiline comment
Merge pull request #1555 from antograssiot/3.0

Typos in comments