fix bug in logging: monitor and actor was logged on stderr

the parent of all logger is now 'mobyle'
the logger name of mobyle2execd is mobyle.mob2execd
remove _class_registery from top level

_class_registery was at top level and exposed to side effect.
move it in a closure

as pyton doe not reexcute code if a module is import twice
modify the behavior if load_execution_system is called twice
fix bug when load_rules is called twice

as pyton doe not reexcute code if a module is import twice
modify the behavior if load_rules is called twice
add default  execution_system or route

if get_dispatcher does not find any  execution system in configuration,
provide a local execution system

if get_dispatcher  does not find any route and there is only one
execution system in configuration provide a default route.
otherwise raise a mobyleError