Moved file and path related methods from StringHelper to FileHelper, renamed StringHelper byte methods not to be misused as string methods

also removed superflous minimum-stability definition

fixes #1146

not needed when installed via composer and application config loads
composer extensions correctly

set alias to the correct path as they are not part of the yii framework
directory anymore

Fixes #1133: gii controller generator now uses application controllerNamespace as default value for "Controller Namespace"

fixes #1131