UCM — the UCM standard platform should reorganized

There should be only 3 standard component execution policies: unprotected_passive, protected_passive and protected_active (they more or less correspond to <nothing>, ppUnit and rtUnit in MARTE). protected_self-executing is actually not an execution policy, but a triggering policy, and should therefore be regrouped with the timers in the additional execution policies

separate self-execution policy from component execution policy

Associate the self-executing component policy to a component execution trigger aspect rather than a component execution aspect. Also associate the timer policies to the execution trigger aspect.