[460947] Support Java Services reloading in AQL

Reworks JavaExtensions to guarantee to always call unload() methods
first on the ClassLoadingcallBacks and then triggers all the loads(). 
Use the dedicated API in Acceleo Query to unregister the service
instances.

Bug: 460947
Change-Id: I165e16f2fa4d6956d74982d198f2dda5bb1387d2
Signed-off-by: Cedric Brun <cedric.brun@obeo.fr>
2 files changed