ecurity improvement: jAuth::logout() can destroy the session if session_destroy=on in the configuration

Did also refactoring on the code about persistant cookie
Fixed jAuth: the new hash method couldn't be used by app that don't use the jauth module
Merge branch 'jelix-1.2.x' into jelix-1.3.x

Conflicts:
	build/manifests/jelix-lib.mn