Revert "Always use error layout when rendering error pages."

This reverts commit 3495422ac5bde8667becaa1e4afc12c9d139c69b.
Only check for existing method expresion() when it actually will be called.
Datasources that use calculate() should not be forced to implement expression() as well
Merge branch '2.1' into 2.2

Conflicts:
	lib/Cake/Test/Case/Model/Datasource/DboSourceTest.php
Fixing eg. code in doc block
Outputs messages of which plugin is going to have locations upgrade.
Merge pull request #601 from luisarmando/infoUpgrade

Outputs messages of which plugin is going to have locations upgrade.
Always reconfigure global state.

Fixes issues wher the test suite with no fixtures could hit
a non test connection.

Fixes #2743
Fix issues loading response classes from plugins.

Fixes #2759
Fragments should not be urlencoded()

encoding them breaks fragments for client side
applications like backbone.js

Fixes #2755
Merge branch '2.1' into 2.2
FormHelper : use the empty option for radio buttons
remove 'empty' option from  once checked
add tests for the 'empty radio option' feature
Coding standards cleanup.

Fix coding standards
Simplify addition of empty.
Add doc block for new feature.
Fix coding standards warnings.
Fix a few code standards errors.
Merge remote-tracking branch 'ceeram/2.2-hash' into 2.2-hash
Fix whitespace and remove duplicate method calls.
Fix notice errors with postgres.
Update doc blocks for CakeNumber.