Improved action filter and action execution flow by supporting installing action filters at controller, module and application levels

Added support to allow an event handler to be inserted at the beginning of the existing event handler list

RBAC: decoupled rules from assignments and items, implemented php manager

removed duplicated joins when using joinWith and via relations

fixes #2650

Fixed UrlManager rules caching

Fixes issue #2978 - JSON MIME type

Fixes #2955: Changed the signature of ActiveQuery constructors and `ActiveRecord::createQuery()` to simplify customizing ActiveQuery classes